ICSE Class 9 Physics

ICSE Class 9 Physics Sample Question Paper 10 with Answers

Section -1
(Attempt all questions from this section)

Question 1.
(a) The size of a particle is 5.2 p. Express it in metre.
(b) State the numerical value of the frequency of oscillation of a second’s pendulum. Does it depend on the amplitude of oscillation ?
(c) In an instrument, there are 25 divisions on the vernier scale which have length of 24 divisions of the main scale. 1 cm on main scale is divided into 20 equal parts. Find the least count.
(d) What are fundamental quantities ? Give examples.
(e) A pendulum makes 80 oscillations in 20 s. Find its frequency and time period.
Answer:
(a) Given: Size of particle = 5.2 μ
Since 1μ =10^-1 m
∴ Size of particle = 5.2 x 10^-6 m.

(b) The frequency of oscillation of a second’s pendulum is 0.5 s. No, it does not depend on the amplitude of oscillation.

(c) The value of one main scale division, x \(\frac{1}{20}\) = cm
The number of divisions on vernier scale, n = 25
∴ Least count of vernier scale = \(=\frac{\text { Value of one main scale division }(x)}{\text { Number of divisions on vernier scale }(n)}\)
\(=\frac{\frac{1}{20}}{25}=\frac{1}{500}=0.002 \mathrm{~cm}\)

(d) Fundamental quantities are those quantities which do not depend upon other quantities. The examples are : Mass, length, time etc.

(e) Given, Oscillations in 20 s = 80
∴ Oscillations in 1 s = \(\frac{80}{20}=4\)
∴ Frequency = 4 Hz
Also \(\text { Time period }=\frac{1}{\text { Frequency }}=\frac{1}{4}=0.25 \mathrm{~s}\)

Question 2.
(a) An athlete takes 3 rounds of a circular field of radius 7 m. Find his distance and displacement.
(b) Why do dust particles from a carpet get removed when hit with a stick ?
(c) A body weighs 75 g in air, 70.5 g in water and 66 g in a liquid. Calculate the relative density of the liquid.
(f) If a stone and a pencil are dropped simultaneously in vacuum from the top of a tower, which of the two will reach the ground first ? Give reason.
(g) What can you say about the nature of motion of a body if its displacement-time graph is
(i) a straight line parallel to time axis ? (ii) a straight line inclined to the time-axis with an acute angle ?
Answer:

Displacement = 0, because initial and final position of the athlete are the same.
(b) When a carpet is hit with a stick, it sets the carpet in motion, whereas the dust particles embedded in it remain in the initial position of rest due to inertia. Thus, the dust particles are removed from the carpet.

(c) Given : Weight of body in air, W = 75.0 g
Weight of body in water, W₁= 70.5 g
Weight of body in liquid, W₂ = 66.0 g

(d) Both, the stone and the pencil will reach the ground simultaneously in vacuum since acceleration due to gravity is same on both.
(e) (i) The body is stationary (or no motion).
(ii) The motion is away from the starting point with uniform velocity.

Question 3.
(a) Why are we looking at alternative sources of energy ?
(b) Name the mirror which always produces an erect and virtual image. How is the size of image related to the size of the object ?
(c) At what maximum distance the image in a convex mirror can be obtained ? What will be the location of the object then ?
(d) State two laws of reflection of light.
(e) Calculate : (i) wavelength, (ii) time period of a tuning fork of frequency 480 Hz, which is set to vibrate. (Take velocity of sound in air as 332 ms^-1.)
Answer:
(a) We are looking at alternative sources of energy mainly due to two reasons :
(1) The fossil fuels and nuclear fuels present in the earth are limited and may not last for long, and
(2) Because of the undesirable effects of pollution both from the burning of fossil fuels and from the radioactive wastes of the nuclear power plants.

(b) A convex mirror always produces an errect and virtual image. The image formed is shorter than the object.

(c) The maximum distance at which an image in a convex mirror can be obtained is the focal length. The location of the object will be at infinity.

(d) A light ray obeys the following two laws of reflection :
(1) The angle of incidence i is equal to the angle of reflection r, i.e., ∠i = ∠r.
(2) The incident ray, the reflected ray and the normal at the point of incidence, lie in the same plane.

Question 4.
(a) Fill in the following blanks with suitable words :
A current is a flow of………………….. for this to happen, there must be a …………..circuit
(b) Name and define the unit of current.
(c) What is meant by saying that the potential difference between two points is 1 V ?
(d) Why does a compass needle get deflected when brought near a bar magnet ?
(e) An electric bulb draws a current of 0.25 A for 10 minute. Calculate the amount of electric charge that flows through the circuit.
Answer:
(a) Electrons, closed.
(b) The S.I. unit of electric current is ampere. When 1 coulomb of charge flows through any cross-section of a conductor in 1 second, the current flowing through it is said to be 1 ampere
(c) The potential difference between two points is said to be 1 volt (IV) if 1 joule of work is done in moving 1 coulomb of electric charge from one point to the other.
(d) A compass needle gets deflected when brought near a bar magnet because the bar magnet exerts a magnetic force on the compass needle which is itself a tiny pivoted magnet capable pf moving in a horizontal plane.
(e) Given : Current, I = 0.25 A, Charge, Q = ?, Time, t = 10 minute = 10 x 60 s = 600 s

Thus, the amount of electric charge that flows through the circuit is 150 C.

Section – II
(Attempt any four questions from this section)

Question 5.
(a) Name three main parts of a screw gauge and state their function.
(b) A particle initially at rest, moves with an acceleration 5 ms^-2 for 5 s. Find the distance travelled in
(i) 4 s (ii) 5 s and (iii) 5th second.
(c) A stone is thrown upwards at 50 ms^-1. Find : (i) the maximum height attained by the stone, (ii) the time taken by the stone to reach back. (Take g = – 10 ms^-2.)
Answer:
(a) Three parts of a screw gauge and their functions are :
(i) Sleeve : To mark main scale and base line.
(ii) Thimble : To mark circular scale.
(iii) Circular scale : Helps to read length correct upto 0.01 mm.

(b) Given : Initial velocity, u = 0, Acceleration, a = 5 ms^-2
(i) Distance travelled in t = 4 s,

(iii) Distance travelled in 5th second = Distance travelled in 5 s – Distance travelled in 4 s

(c) Given : u = 50 m/s, g = – 10 m/s², ν = 0
(i) ν² = u² + 2gh
0 – (50)² + 2 x (-10) x h

Question 6.
(a) (i) What is ultrasound ?
(ii) State two properties of ultrasound that make it useful to us.

(b) (i) What do you mean by audible range of frequency ?
(ii) What is the audible range of frequency for a human ?
(iii) For which range of frequencies are human ears most sensitive ?

(c) How do the following factors affect, if at all, the speed of sound in air :
(i) Frequency of sound,
(ii) Temperature of air
(iii) Pressure of air
(iv) Moisture in air.
Answer:
(a) (i) Sound of frequency greater than 20 kHz is known as ultrasound.
(ii) The two properties of ultrasound that make it useful to us are :
(1) High energy content, and (2) High directivity.

(b) (i) The range of frequency within which the sound can be heard by a human being is called the audible range of frequency.
(ii) The audible range of frequency for humans is 20 Hz to 20 kHz.
(iii) Human ears are most sensitive to frequencies between 2000 Hz to 3000 Hz.

(c) (i) No effect
(ii) Speed of sound increases with increase in temperature.
(iii) No effect
(iv) Speed of sound increases with increase of moisture in air.

Question 7.
(a) Name the type of mirror used in the following situations :
(i) Headlights of a car
(ii) Side/rear view mirror of a vehicle
(iii) Solar furnace.

(b) State the rules for drawing geometric images in concave mirrors.

(c) An object is placed at the following distances from a concave mirror of focal length 15 cm, turn by turn : (1) 35 cm, (2) 30 cm, (3) 20 cm, (4) 10 cm.
Which position of the object will produce :
(i) a magnified real image ?
(ii) a magnified virtual image ?
(iii) a diminished real image ?
(iv) an image of same size as the object ?
Answer:
(a) (i) A concave mirror is used in the headlights of a car.
(ii) A convex mirror is used as the side/rear view mirror of a vehicle.
(iii) A concave mirror is used in a solar furnace.

(b) Rules for drawing geometric images in concave mirror are :
(1) Any ray of light travelling parallel to the principal axis of a concave mirror, after reflection passes through the principal focus of the mirror.
(2) Any ray of light which first passes through the principal focus, after reflection, will travel parallel to the principal axis of a concave mirror.
(3) A ray of light which first passes through the centre of curvature of a concave mirror after reflection will retrace its path.

(c) (i) 20 cm, (ii) 10 cm, (iv) 35 cm, (iv) 30 cm.

Question 8.
(a) (i) What do you understand by thermal expansion of a substance ?
(ii) Name two substances which contract on heating.
(b) State three differences between temporary and permanent magnets.
(c) State four advantages of using biogas as fuel.
Answer:
(a) (i) The expansion of a substance on heating is called the thermal expansion of that substance.
(ii) Two substances that contract on heating are : water from 0°C to 4°C, and silver iodide from 80°C to 141°C.

(b)

Temporary Magnet	Permanent Magnet
They are made of soft iron.	They are made from steel.
They behave like a magnet only as long as there is an inducing magnet.	They act as a magnet even on the removal of the inducing magnet.
They have very poor magnetic retention.	They have a very high magnetic retention.

(c) Four advantages of using biogas as fuel are as follows :
(1) Biogas is an excellent fuel which can be used for cooking.
(2) Biogas does not produce any smoke and hence, helps in cutting down air pollution.
(3) Biogas, on burning, leaves behind no ash.
(4) The calorific value of biogas is very high.

Question 9.
(a) (i) What is a real image ?
(ii) What type of mirror can be used to obtain a real image of an object ?
(iii) Does the mirror mentioned in part (ii) form real image for all locations of the object ?

(b) (i) At what temperature, the density of water is maximum ? State its value.
(ii) Draw a graph to show the variation in density of water with temperature in the temperature range from 0°C to 10°C.

(c) A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object from the lens ?
Answer:
(a) (i) A real image is one which can be obtained on a screen.
(ii) A concave mirror can be used to obtain a real image of an object.
(iii) No, it forms a virtual image if the object is placed between the focus and pole of the mirror.

(b) (i) The density of water is maximum at a temperature of 4°C and its value is 1000 kg m³.
(ii) The graph showing variation in density of water with temperature in range 0°C to 10°C is shown below.

(c) Given : Object distance, u = ?
Image distance, ν = – 10 cm
Focal length, f= – 15 cm
Putting these values in the lens formula :

Thus, the object is placed at a distance of 30 cm from the concave lens. The minus sign with the object distance shows that the object is on its left side, i.e., in front of mirror.

Question 10.
(a) A small magnet is suspended by a silk thread from a rigid support such that the magnet can freely swing. How will it rest ? Draw a diagram to show it.
(b) Calculate the mass of the earth, assuming it to be a sphere of radius 6370 km. (Take G = 6.67 x 10^-11 Nm² kg^-2 and g = 9.80 ms^-2.)
(c) The given figure shows the magnetic field between two magnets.
Answer:
(a) It will rest in the geographic north-south direction with north pole towards the geographic north, making some angle with the horizontal as shown in the figure.

(b)

ICSE Class 9 Physics Question Papers with Answers

ICSE Class 9 Physics Sample Question Paper 9 with Answers

Section -1
(Attempt all questions from this section)

Question 1.
(a) Name four fundamental quantities.
(b) Name the instrument which has the least count: (i) 0.1 mm, (ii) 0.01 mm.
(c) Two simple pendulums A and B have equal length, but their bobs weigh 150 gf and 200 gf respectively. What would be the ratio of their time periods ? Give reason for your answer.
(d) Two simple pendulums P and Q have length 4 m and 9 m respectively at a certain place. Which pendulum will have more oscillations in 1 minute ? Explain your answer.
(e) If time periods of two pendulums are in the ratio of 3 : 5, find the ratio of their lengths.
Answer:
1. (a) Length, mass, time and temperature are examples of fundamental quantities.

(b) (i) Vernier callipers (ii) Screw gauge.

(c) The ratio of the time periods of pendulums A and B is 1 : 1. This is because time period does not depend on the weight of the bob.

(d) Since time period is directly proportional to the square root of effective length, \((\mathrm{T} \propto \sqrt{l})\)
the time periods of P and Q are 2 sec \((\sqrt{4})\) and 3 sec \((\sqrt{9})\) respectively. Clearly P will complete 30 oscillations and Q will only complete 20 oscillations in 1 minute. Hence, pendulum P makes more oscillations.

Question 2.
(a) A body starts from rest and moves for 5 seconds. It accelerates uniformly and its velocity changes to 25 m/s. Find the acceleration of the body.
(b) According to Newton’s third law, every force is accompanied by an equal and opposite force. How can a movement ever take place ?
(c) Why is Newton’s law of gravitation known as the universal law ?
(d) Select the scalars and vectors from the following : time, distance, acceleration, work, mass, force.
(e) “The value of ‘g’ remains same at all places on the earth’s surface.” Is this statement true ? Give reason for your answer.
Answer:
(a) Given : u = 0 (body starts from rest), t = 5 s, v = 25 ms^-1
\(a=\frac{v-u}{t}=\frac{25-0}{5}=5 \mathrm{~ms}^{-2}\)

(b) Action and reaction do not act on the same body, but act on different bodies and, hence motion is possible.

(c) Newton’s law of gravitation is known as the universal law of gravitation because it is applicable to all masses at all distances and is not affected by the medium between the two masses.

(d) Scalars : distance, work, time, mass.
Vectors : acceleration, force.

(e) No, the value of g does not remain same at all places on the earth’s surface. The value of g is maximum at the poles and minimum at the equator. This is because, it varies with the radius of earth at different places, it being maximum at equator and minimum at the poles.

Question 3.
(a) The rear view mirror of a car is plane mirror. A driver is reversing his car at a speed of 3 m/s. The driver sees in his rear view mirror, the image of a truck parked behind his car. What will be the speed at which the image of the trunk appears to approach the driver?

(b) A ray of light is incident normally on a plane mirror. What will be the :
(i) angle of incidence ?
(ii) angle of reflection ?

(c) Name the two types of spherical mirrors. What type of mirror is represented by the :
(i) back side of shining steel spoon ?
(ii) front side of a shining steel spoon ?

(d) Why do we prefer a convex  mirror as a rear-view mirror in vehicles?

(e) Fill in the blanks :
A concave mirror ……………………….  rays of light whereas a convex mirror …………………………….. rays of light.
Answer:
(a) In a plane mirror, the object and its image always remain at the same distance from the mirror. So when the car reverses at a speed of 3 m/s, then the image will also appear to move towards the mirror at the same speed of 3 m/s. So, the speed at which the image of the truck appears to approach the car driver will be 3 m/s + 3 m/s = 6 m/s.

(b) (i) Angle of incidence = 0° (ii) Angle of reflection = 0°

(c) (i) Convex mirror (ii) Concave mirror.

(d) We prefer a convex mirror as a rear-view mirror in vehicles because of the following reasons :
(i) A convex mirror always produces an erect image of the object.
(ii) The image formed in a convex mirror is much smaller than the object, due to which a convex mirror gives a wide field of view (of the traffic behind).

(e) Converges, diverges

Question 4.
(a) Which has more resistance :
(i) A long piece of nichrome wire or a short one ?
(ii) A thick piece of nichrome wire or a thin one ?

(b) Copy the given figure which shows a plotting compass and a magnet. Label the N pole t of the magnet and draw the field line on which the compass lies.

(c) What does an electric circuit mean?
(d) Calculate the number of electrons constituting one coulomb of charge.
(e) How much work is done in moving a charge of 2 Colomb from a point at 95 volt to a point at 105 volt?
Answer:
(a) (i) Long piece of nichrome wire; (ii) Thin piece of nichrome wire.
(b) The completed diagram of the compass and magnet is as follows :

(c) A continuous conducting path consisting of wires and other resistances (like electric bulb, etc.) and a switch, between the two terminals of a cell or battery, along which an electric current flows, is called an electric circuit.

(d) Charge of an electron is 1.6 x 10^-19
If charge is 1.6 x 10^-19 C, then no. of electrons = 1
So, if charge is 1 C, the number of electrons

Thus, 6.25 x 10¹⁸ electrons taken together constitute 1 coulomb of charge

(e)

Section – II
(Attempt any four questions from this section)

Question 5.
(a) State three requirements for selecting a unit of a physical quantity.
(b) A ball falls from the top of tower of height 19.6 cm. Find the time of fall and velocity of the ball when it reaches the ground, (g = 8 m/s²)
(c) Name four parts of a vernier callipers and state their functions.
Answer:
(a) Requirements of standard unit are :
(1) It should be well defined.
(2) It should be easily reproducible at all places.
(3) It should not change with time, and from place to place

(b) Given : u = 0, h =6 m, g = 9.8 ms^-2
v² = u² + 2gh v
\(v=\sqrt{2 \times 9.8 \times 19.6}\)

(c) The four parts of a vernier callipers along with their functions are :
(1) Outside jaws : To measure the length of a rod, diameter of a sphere, external diameter of a hollow cylinder etc.
(2) Inside jaws : To measure the internal diameter of a hollow cylinder or pipe.
(3) Strip : To measure the depth of a beaker or a bottle.
(4) Vernier scale : Helps to measure length correct upto 0.1 mm.

Question 6.
(a) Show that : Rate of change of momentum = Mass x Acceleration.
(b) Two balls A and B of masses ‘m’ and ‘2m’ are in motion with velocities 2v and v
Compare : (i) their inertia, (ii) their momentum and (iii) the force needed to stop them in the same time.
(c) A cricket ball of mass 100 g moving with a speed of 40 ms^-1 is brought to rest by a player in 0.04 s.
Find : (i) the change in momentum of ball,
(ii) the average force applied by the player.
Answer:
(a) Let a force ‘F’ be applied on a body of mass ‘m’ for time T due to which its velocity changes from ‘u’ to ‘ν’. then,
Initial momentum of the body = mu
Final momentum of the body = mv
Change in momentum of the body in t second = mv – mu = m (υ – u)

(c) Given: m 100g= kg=\(\frac{100}{1000}\) 0.1kg ,u=40ms^-1 v = 0,t = 0.04s.
(i) Initial momentum mu = 0.1 x 40 = 4.0 kg ms^-1
Final momentum = mv =1 x 0 = 0
∴ Change in momentum = Final momentum – Initial momentum
= 0 – 4 = – 4kg ms^-1
Change in momentum

(ii) Average force, \(\text { Average force, } \mathrm{F}=\frac{\text { Change in momentum }}{\text { Time }}\)
\(=\frac{-4}{0.04}=-100 \mathrm{~N}\)
The negative sign here shows that the force is applied in a direction opposite to the direction of motion of the ball.

Question 7.
(a) A man standing in front of a special mirror finds his image having a very small head, a fat body and the legs of normal size. What are the shapes of the three parts of the mirror ?
(b) An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
(c) When a spherical mirror is held towards the sun and its sharp image is formed on a piece of carbon paper for some time, a hole is burnt in the carbon paper.
(d) What is the nature of the spherical mirror ?
(e) Why is a hole burnt in the carbon paper ?
(f) At which point of the spherical mirror is the carbon paper placed ?
(g) What name is given to the distance between the spherical mirror and carbon paper ?
Answer:
(a) The top part of the special mirror is convex as it produces a small image of the head. The middle part of the mirror is concave as it produces a magnified image of the body. The lower part of the mirror is a plane mirror as it produces the image of the same size.

(b) Given : Object distance, u = – 10 cm
Image distance, ν = ?
Focal length, f = 15 cm

So, image distance, v = 6 cm. Thus, the position of image is at a distance of 6 cm from the convex mirror on its right (behind the mirror) since the image is formed behind the convex mirror, therefore, the nature of image is virtual and erect.

(c) (i) Concave mirror,
(ii) A lot of sun’s heat rays are concentrated at the point which bum the hole in carbon paper
(iii) At the focus
(iv) Focal length.

Question 8.
(a) State three conditions for the propagation of sound.
(b) State three uses of ultrasonic vibrations.
(c) A student made an electric circuit shown below to measure the current through two lamps.

(i) Are the lamps in series or parallel ?
(ii) The student has made a mistake in this circuit. What is it ?
(iii) Draw a diagram to show the correct way to connect the circuit. Use the proper circuit symbols in your diagram.
Answer:
(a) Conditions for the propagation of sound are :
(1) There must be a vibrating body, capable of transferring energy.
(2) There must be a material medium, through which energy can propagate.
(3) There must be a receiver (ear), so as to receive and transmit the energy to the brain.

(b) Ultrasonic vibrations are used in
(1) Dissipating of fog,
(2) Ultrasound welding, and
(3) Ultrasound scanning of the human body.

(c) (i) In series.
(ii) Ammeter is connected in parallel with the lamps. It should be connected in series.
(iii) The corrected diagram is :

Question 9.
(a) State the rules for drawing geometric images in convex mirrors.
(b) Write three equations of uniformly accelerated motion relating the initial velocity (u), final velocity (ν), time (t), acceleration (a) and displacement (s).
(c) Waves A and B as shown in the figure, propagate in the same medium. Frequency of wave A is 5000 Hz. Find the velocity of both waves and frequency of wave B.

Answer:
Rules for drawing geometric images in convex mirrors :
(1) Any ray of light, travelling parallel to the principal axis of convex mirror, after reflection, appears to pass through the principal focus of the mirror.
(2) Any ray of light travelling along the principal focus of convex mirror, aftrer reflection, travels parallel to the principal axis.
(3) Any ray of light travelling along the centre of curvature of a convex mirror, after reflection, retraces its path.

(b) The three equations of motion are :

Question 10.
(a) You are required to make an electromagnet from a soft iron bar by using a cell, an insulated coil of copper wire and a switch. Draw a circuit diagram to represent the process and label the poles of the electromagnet.

(b) You are given a resistance wire PQ connected with a cell and a key as shown in the given figure. You are required to measure the current in the wire PQ and potential difference across it. Name the instruments that you would use and draw a labelled diagram to show how are they connected. Also, mark the direction of current in each component.

(c) A boy measures the length of a piece of pencil by meter rule, vernier callipers and screw gauge to be 7.3 cm, 7.35 cm and 7.353 cm respectively. State (i) the least count of each measuring instrument, (ii) the accuracy in each measurement.
Answer:
(a) The required circuit diagram is :

(b) An ammeter is used to measure current and a voltmeter is used to measure the potential difference. The ammeter (A) is corrected in series with the resistance wire PQ and cell, while the voltmeter (V) is connected in parallel across the wire PQ.

(c) (i) Least count of meter rule = 0.1 cm
Least count of vernier callipers = 0.01 cm
Least count of screw gauge = 0.001 cm.

(ii) Accuracy in 7.3 cm = 0.1 cm
Accuracy in 7.35 cm = 0.01 cm
Accuracy in 7.353 cm = 0.001 cm.

ICSE Class 9 Physics Question Papers with Answers

ICSE Class 9 Physics Sample Question Paper 8 with Answers

Section -1
(Attempt all questions from this section)

Question 1.
(a) The bob of a simple pendulum is made of wood. What will be the effect on the time period if an identical bob of aluminium replaces the wooden bob ?
(b) (i) The linear distance moved by the screw, when it is given one complete rotaion is
equal to the distance between two consecutive threads, as measured along the axis of the screw. This distance is called ………………….. the of the screw.
(ii) The least count of a screw is defined as the distance moved by the screw on the main scale when the screw is given ………………….. complete revolution/s.
(c) What happens when you shake a wet piece of cloth ? Explain your observation.
(d) A bag of sugar weighs ‘W’ at some place on the equator. If this bag is taken to the poles, will it weigh the same, more or less ? Give a reason for your answer.
(e) A body of mass 500 g is at rest on a frictionless surface. Calculate the distance travelled by it in 10 s when acted upon by a force of 10^-2 N.
Answer:
(a) There is no change in the time period of the simple pendulum because though the wooden bob is replaced by the aluminium bob, the effective length of the pendulum remains the same. Since the time period of a simple pendulum does not depend on the mass of the bob, it remains unaltered.

(b) (i) Pitch, (ii) One

(c) Initially, the piece of cloth and the loose water in it are in a state of rest. When the cloth is shaken, it is suddenly set into motion. However, the water in it, on account of inertia of rest, continues its state of rest. Thus, water comes out of the cloth in the form of fine particles.

(d) The bag of sugar will weigh more at the poles. The reason for this is, the polar radius of the earth is less than the equatorial, radius of the earth. The acceleration due to gravity is inversely proportional to the square of the radius of the earth. Hence, its value at the poles is greater than its value at the equator. Since weight is the product of mass and acceleration due to gravity, therefore, the bag of sugar will weigh more at the poles.

(e) Given : m = 500 g = 0.5 kg, t = 10 s , F = 10^-2 N 0.01 N, u = 0
Using  F – ma,
we have,

Question 2.
(a) Why are two holes made in an oil tin to remove oil from it ?
(b) A piece of ice is gently placed on the surface of water filled in a glass tumbler, so the water rises to the brim. What will happen to the level of water when the ice melts ? Will the water overflow ? If not, explain with reason.
(c) State two advantages of L.P.G.
(d) Why are taps left dripping in sub-zero temperature during winter ?
(e) The base of a cylindrical vessel measures 300 cm². Water is poured into it upto a depth of 6 cm. Calculate the pressure and thrust on the base. (Take density of water = 103 kg m^-3 and g = 10 ms^-2.)
Answer:
(a) If a single hole is made in the oil tin, the oil will not flow out because the pressure inside the tin becomes less than the atmospheric pressure. In order to force oil out, two holes are made. Thus, air enters from one hole, exerts pressure on the oil, and forces ìt out from the other hole.

(b) Since ice floats in water, its weight is equal to the weight of displaced water. Suppose ice weighs ‘m’ gf, then the weight of displaced water will also be ‘m’ When the ice melts, m gf of water is obtained which is equal to the weight of displaced water, so there will be no change in the level of water, and the water does not overflow.

(c) Two advantages of L.P.G. are as follows :

• It is easy to handle and convenient to store.
• It does not produce harmful gases on burning.

(d) The taps are left dripping during winter to provide sufficient space for expansion of freezing water due to its anomalous expansion. If this is not done, the freezing water will exert large pressure on the tap and there are chances that it may burst.

(e) Given : h = 6 cm = 6 x 10^-2 m, A = 300 cm² = 3 x 10^-2 m² , density of water= 1000 kgmr³, g = 10 m/s²
We know,
Pressure, P = hρg
= 6 x 10^-2 x 1000 x 10
= 600 Pa.
Thrust, F = P x A
= 600 x 3 x 10^-2 = 18 N

Question 3.
(a) Can a plane as well as a convex mirror produce real image if the object is virtual ? Explain.
(b) Complete the following sentences :
(i) A ray of light parallel to the principal axis of a convex mirror seems to come from
the after reflection.
(ii) A concave mirror forms an erect image when the object is placed between the focus
and the
(c) State the laws of reflection of light.
(d) What is the range of frequencies associated with (i) Infrasound, and (ii) Ultrasound ?
(e) A submarine emits a sonar pulse, which returns from an underwater cliff in 1.2 s. If the speed of sound in salt water is 1460 ms^-1, how far away is the cliff ?
Answer:
(a) Yes, a real image can be obtained from both plane mirror and convex mirror if the object is virtual and behind the mirror. This can be done by making a converging beam of light fall on the mirror. The converging beam forms a virtual object behind the mirror, producing a real image in front of the mirror.

(b) (i) Focus
(ii) Pole

(c) The laws of reflection of light are :
(1) The angle of incidence (i) is equal to the angle of reflection (r).
(2) The incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane.

(d) (i) Infrasound waves are between the frequencies 1 to 20 Hz.
(ii) Ultrasound waves are of the frequencies above 20000 Hz.

(e) Given : t = 1.2 s; ν – 1460 ms^-1, S = ?

Question 4.
(a) Define electric current. Name its S.I. unit.
(b) Fill in the blanks :
A cell cannot be recharged whereas a cell can be recharged.
(c) Name two types of cells.
(d) What do you mean by magnetic field of a magnet ?
(e) Define magnetic pole of the Earth.
Answer:
(a) Electric current is defined as the rate of flow of charge through a certain cross-section of a conductor in a particular direction. Its S.I. unit is ampere (A).
(b) Primary, secondary.
(c) Two types of cells are — Primary cells and secondary cells.
(d) The region around a magnet in which its magnetic force can be experienced by another magnetic substance is called magnetic field of the magnet.
(e) The point on the earth where a magnetic needle points vertically is called the magnetic pole.

Section – II
(Attempt any four questions from this section)

Question 5.
(a) A large truck and a car, both moving with speed V, have a head on collision and both of them come to halt after that. If the collision lasts for 10 s,
(i) Which vehicle experiences the greater force of impact ?
(ii) Which vehicle experiences the greater momentum change ?
(iii) Which vehicle experiences the greater change in acceleration ?
(b) The acceleration due to gravity at the moon’s surface is 1.67 ms^-2. If the radius of the moon is 1.74 x 106 m, calculate the mass of the moon. Use the known value of G.
(c) The main scale of a vernier calliper is caliberated in mm and 19 divisions of main scale are equal in length to 20 divisions of vernier scale. In measuring the diameter of a cylinder by this instrument, the main scale reads 35 divisions and 5th division of vernier scale coincides with a main scale division, find the (i) least count, (ii) diameter of the cylinder.
Answer:
(a) (i) Both the vehicles experience same force of impact as action and reaction are equal and opposite in both cases.
(ii) The truck experiences a greater change in momentum on account of its greater mass.
(iii) The car experiences greater change in acceleration as force remaining same, acceleration is inversely

Question 6.
(a) Mention any three areas where solar cells are being used as a source of energy.
(b) State three limitations of solar energy.
(c) A balloon of volume 50 m³ is filled with hot air of density 0.4 kg m². If the weight of the fabric of the balloon is 12 kgf and equipment ‘P’ is attached to it, such that balloon is in the state of equilibrium, calculate (i) weight of hot air, (ii) weight of hot air, balloon and equipment, (iii) upthrust, and (iv) weight of equipment. (Density of normal air = 1.3 kg / m³)
Answer:
(a) Three areas where solar cells are being used as energy are :
(1) Artificial satellites
(2) Radio or wireless transmission
(3) Traffic lights.

(b) Three limitations of solar energy are as follows :
(1) Solar energy is not available at a constant rate due to clouds, wind, haze, etc.
(2) Solar energy is not available at night uniformly.
(3) Solar energy may not be available at all places on the earth.

(c) (i) Weight of hot air = Volume of balloon x Density of hot air x g
= 50 x 0.4 x g = 20 kgf

(ii) Weight of (Hot air + Balloon + Equipment)
= 20 + 12 + P = (32 + P) kgf

(iii) Upthrust = Weight of air displaced
= Volume of balloon x Density of air x g = 50 x 1.3 x g = 65 kgf

(iv) By law of floatation, we have
32 + P = 65
P = 65 – 32 = 33 kgf.

Question 7.
(a) Define the following terms related to spherical mirrors :
(i) Principal axis, (ii) Focal plane, (iii) Focal length.
(b) An object of size 5 cm is placed at a distance of 24 cm in front of a concave mirror of focal length 16 cm. At what distance from the mirror should a screen be placed so as to obtain a sharp image of the object ? Find the nature of the image.
(c) State four uses of concave mirror.
Answer:
(a) (i) The straight line passing through the pole and the centre of curvature of the mirror is called the principal axis.
(ii) A plane drawn perpendicular to the principal axis and passing through the principal focus is called the focal plane.
(iii) The distance between the pole and the focus is called the focal length. It is represented by

(b) Given : h = 5 cm, u = – 24 cm, f = – 16 cm, v = ? , h’ = ?

The image is formed 48 cm in front of the mirror. Thus, the image is real and inverted. Thus, the screen should be held 48 cm in front of the mirror.

(c) Concave mirrors are used for the following purposes :
(i) Reflecting mirror for projector lamps.
(ii) In torches and head lights.
(iii) In a shaving mirror, and
(iv) It is used to concentrate sunlight in solar farms.

Question 8.
(a) What are mechanical or elastic waves ? Name its two types.
(b) A body is vibrating 60000 times in one minute. If the velocity of sound in air is 340 ms^-1,
find (i) frequency of the vibration in Hz
(ii) wavelength of the sound produced. Also,
(iii) ………. can this sound be heard by human beings ?
(c) State four uses of ultrasound.
Answer:
(a) A mechanical wave is a distubance that travels through some material medium or substance called the medium of the wave.
It has two types : (1) Transverse waves and (2) Longitudinal waves.

(b) Given : Number of vibrations = 60000, time (t) = 1 min = 60 s, velocity (ν) = 340 ms^-1

(iii) Here, f = 1000 Hz, hence it can be heard by human beings, (c)
(c) Ultrasound is used for the following purposes :
(1) To monitor the growth of a foetus (unborn baby).
(2) To investigate the internal organs of human body.
(3) To break kidney stones into fine grains.
(4) To remove brain tumour.

Question 9.
(a) (i) What is a secondary cell ?
(ii) State two advantages of a secondary cell over a primary cell.
(b) (i) What do you mean by efficient use of energy ?
(ii) How can energy efficiency be achieved ?
(c) Draw the circuit symbols of the following :
(i) Cell
(ii) Fixed resistance
(iii) Switch
(iv) Ground.
Answer:
(a) (i) A secondary cell is one in which chemical energy is converted into electrical energy but they do so only when they are charged by passing current through them by some source.
(ii) Advantages of secondary cell over primary cell are :
(1) A secondary cell can be put to use again and again by recharging it; while a primary cell once discharged, cannot be charged again.
(2) The internal resistance of a secondary cell is less than that of the primary cell. As such, a much larger current can be drawn from a secondary cell than that can be drawn from a primary cell.

(b) (i) Efficient use of energy refers to the reduction of cost and amount of energy used in order to provide various products and services.
(ii) Energy efficiency can be achieved by adopting more efficient eco-friendly technologies and processes.

Question 10.
(a) (i) Define resistance.
(ii) A cell is connected to a bulb which develops a potential difference of 6 volt across it. The current in circuit is measured to be 2 ampere. Find the resistance offered by the filament of bulb to the flow of current.
(b) Draw a neat labelled diagram of an electric bell.
(c) State four evidence to show the existence of earth’s magnetic field.
Answer:
(a) (i) The obstruction offered to the flow of current by the wire is called its electrical resistance.
(ii) Given : V = 6 volt, I = 2 ampere
Resistance of filament of bulb, R =y \(\begin{aligned}
\mathrm{R} &=\frac{\mathrm{V}}{\mathrm{I}} \\
&=\frac{6}{2}=3 \mathrm{ohm}
\end{aligned}\)

(b)

(c) The existence of earth’s magnetic field is based on the following facts :
(1) An iron rod buried inside the earth along north-south direction becomes a magnet.
(2) A magnetic needle rests with its geometric axis making different angles with horizontal when suspended at different places on earth.
(3) A freely suspended magnetic needle always rest in geographic north-south direction.
(4) Neutral points are obtained on plotting the field lines of a magnet where the net magnetic field is zero.

ICSE Class 9 Physics Question Papers with Answers

ICSE Class 9 Physics Sample Question Paper 7 with Answers

Section -1
(Attempt all questions from this section)

Question 1.
(a) The bob of a simple pendulum is hollow with a pinhole at its lower end. It is filled with water and allowed to oscillate. How does its time period vary with time ?
(b) Fill in the blanks :
(i) Length of a simple pendulum is the distance between the point of………………………….. and the point of oscillation.
(ii) A second’s pendulum is one, whose time period is………………………………. second (s).
(c) A boy running a race accelerates at 2.5 ms^-2 for the first 4 s of the race. How far does he travel in this time
(d) Explain why some of the leaves may fall from a tree, if we vigorously shake its branch.
(e) When dropped from the same height, a body reaches the ground quicker at the poles than at the equator. Why ?
Answer:
(i) As the water drips away from the pinhole, the centre of gravity of the pendulum gets lowered. This increases the effective length of the simple pendulum. Since the time period of a pendulum depends directly on its length, there is an increase in the time period of the simple pendulum in the beginning.

(b)
(i) Suspension
(ii) Two

(c) Given : u = 0 , a = 2.5 ms^-2, t = 4 s , s = ?
We know,
s = ut + \(\frac{1}{2}\) at²
∴ s = 0 x 4 + \(\frac{1}{2}\) 2.5 x 4²  = 20 m.
Thus, the boy travels 20 m in this time.

(d) When the branch of a tree is shaken, it is suddenly set in motion. However, the leaves attached to it tend to continue to be iii their state of rest on account of inertia of motion. Thus, a lot of strain acts on the junction of the leaves and the branches. Due to this strain, the weakly held leaves are left behind, and fall of the branch.

(e) The acceleration due to gravity is greater at the poles than at the equator. When the initial velocities and the distance travelled are the same, time taken for a body is smaller if the acceleration due to gravity is more. Thus, when dropped from the same height, a body reaches the ground quicker at the poles than at the equator.

Question 2.
(a) Why does an ink pen start leaking at higher altitudes ?
(b) A dead body floats, with its head immersed in water. Explain.
(c) State two advantages of biogas.
(d) Why does a glass bottle completely filled with water and tightly capped bursts, when placed in a freezer ?(e) A hydraulic lift is given in the figure. The narrow piston area Aj is 5 cm² and the wide piston area A₂ is 50 cm². If the weight of the block W = 800 N, find the magnitude of force F required to lift up the block W.

Answer:
(a) When the atmospheric pressure on high altitudes decreases, the air present within the tube of ink pen at higher pressure, forces the ink out. As a result, the ink pen starts leaking.

(b) Dead bodies float on water but the head is always immersed. This is because when a dead body decays, its volume increases. Thus, it becomes lighter than water and hence, floats. However, the head being heavy, cannot displace water more than its own weight. Hence, it remains under water.

(c) Advantages of biogas are as follows :
(1) Biogas has a large calorific value.
(2) Biogas can be supplied directly through pipes and hence, has no storage problems.

(d) The water in a glass bottle expands below 4°C due to anomalous expansion of water. Since there is no space provided inside the bottle for this expansion, and if the bottle is tightly capped, it bursts when placed in the freezer.

(e) Given

Question 3.
(a) A ray of light XY is incident on a spherical mirror as shown in the given diagram. Redraw the diagram and mark the normal, angle of incidence and angle of reflection.
(b) Complete the following sentences :
(i) In search light the reflector is a……………………………
(ii) A real and enlarged image can be obtained with a……………………..
(c) What is the difference between virtual images produced by concave, plane and convex mirrors.
(d) Why are sound waves called mechanical waves ?
(e) Calculate the wavelength of a sound wave whose frequency is 160 Hz and speed is 320 ms^-1 in a given medium.

Answer:
(a) The incident ray XY which is parallel to the mirror, after reflection, passes through the focus. This is shown in the given figure. Here CY is the normal at the point of incidence, and Zz and Zr represent the angles of incidence and reflection respectively.

(b) (i) Concave
(ii) Concave                                                                         

(c) A virtual image produced by a concave mirror is magnified, that produced by plane mirror is of the same size, while virtual image produced by a convex mirror is diminished.

(d) Some mechanical energy is required to make an object vibrate. Sound energy cannot be produced on its own. The mechanical energy of vibrating objects travel through a medium and finally reaches the ear. Therefore, sound waves are called mechanical waves.

(e) Given : Frequency = 160 Hz, speed of sound – 320 ms^-1
We know,
Speed of sound = Frequency x Wavelength
∴ \(\text { Wavelength }=\frac{\text { Speed of sound }}{\text { Frequency }}=\frac{320}{160}=2 \mathrm{~m}\)

Question 4.
(a) Name two requirements of a good cell.
(b) Fill in the blanks :
(i) Electric current is defined as the…………………………. through a certain cross-section of a conductor in a particular direction.
(ii) When we draw a circuit diagram, the various elements of a circuit are represented with the help of their……………..
(c) Give two examples of secondary cells.
(d) Define magnetic induction.
(e) What is an electromagnet ?
Answer:
(a) Two requirements of a good cell are :
(1) A good cell must have a large and steady e.m.f.
(2) It should have a low internal resistance.

(b) (i) Rate of flow of charge (ii) Symbols.

(c) Two examples of secondary cells are (1) Lead acid cell and (2) Edison alkali cell.

(d) The magnetism acquired by an unmagnetised magnetic material when it is kept near or in contact with a magnet, is called induced magnetism and the phenomenon is called magnetic induction.

(e) An electromagnet is a coil of wire wound around a soft iron core. It behaves as a permanent magnet except that it can be turned off.

Section – II
(Attempt any four questions from this section)

Question 5.
(a) State three differences between distance and displacement.
(b) The driver of a train travelling at 40 ms^-1 applies the brakes as a train enters a station. The train slows down at a rate of 2 ms^-2. The platform is 400 m long. Will the train stop in time ?
(c) A screw gauge has a negative error of 7 divisions. While measuring the diameter of a wire, the reading on the main scale is 2 divisions with the 79th circular scale division coinciding with the base line. If the main scale has 10 divisions to a centimetre and the circular scale 100 divisions, calculate :
(i) Pitch
(ii) Least count
(iii) Observed diameter
(iv) Corrected diameter.
Answer:

Distance	Displacement
1. Distance is the length of the actual path traversed between its initial and final positions. 2. It is a scalar quantity. 3. It can never be negative.	1. Displacement is the shortest path between the initial and final positions of the particle. 2. It is a vector quantity. 3. It can be positive, negative or zero.

(iii) Observed diameter of wire = Main scale reading + L.C. x CSD coinciding
=0.2+0.001×79
= 0.279 cm.

(iv) Negative error = 7 divisions
Negative correction = LC x 7 division
= 0.001 x 7 = 0.007 cm
Corrected diameter = 0.279 + 0.007 = 0.286 cm.

Question 6.
(a) Why is it not possible to make use of solar cells to meet all our energy needs ? State three reasons to support your answer.
(b) What is non-renewable energy ? Give two examples.
(c) A solid weighs 15 gf in air and 13 gf when completely immersed, in a liquid of relative density 0.8. Find : (i) The volume of solid, and
(ii) Relative density of solid.
Answer:
(a) The following factors prevent the use of solar cell panels to meet all our domestic needs of electricity :
(1) High cost of installation.
(2) Limited availability of special grade silicon to make solar cells.
(3) Tecnnology to obtain pure silicon is too expensive.

(b) The sources of energy which have been accumulated in nature over a very long time (millions of years) and cannot be quickly replaced if once exhausted are called non¬renewable sources of energy.
For example, fossil fuels like coal and petroleum.

(c) (i) Let ‘V’ be the volume of the solid.
Weight of liquid displaced = Volume of liquid displaced x Density of liquid x g
= V x 0.8 gf
Loss in weight of the solid when immersed in liquid = 15 – 13 = 2 gf
But, the weight of liquid displaced = Loss in weight of solid when immersed in liquid
V x 0.8 gf = 2
Or \(\mathrm{V}=\frac{2}{0.8}=2.5 \mathrm{~cm}^{-3}\)

(ii) \(\text { Density of solid }=\frac{\text { Mass }}{\text { Volume }}=\frac{15}{2.5}=6 \mathrm{~g} \mathrm{~cm}^{-3}\)
∴ Relative density of solid is 6.

Question 7.
(a) State three uses of convex mirrors.
(b) An object 3 cm high is placed at a distance of 6 cm from a concave mirror of focal length 12 cm. Calculate the position of the image formed.
(c) State four characteristics of image formed by a plane mirror.
Answer:
(a) Three uses of convex mirrors are :
(1) It is used as a rear view mirror in automobiles.
(2) It is used as a reflector in street lamps so as to diverge light over a large area.
(3) It is also used as a security mirror in shops.

(b) Given : u = – 6 cm, f = – 12 cm, ν= ?
Using mirror formula and substituting the values in it, we have :

The image is formed 12 cm behind the concave mirror.

(c) Characteristics of image formed by a plane mirror are :
(1) The image is of the same size as the object, vitual and erect.
(2) The image has right-left reversal.
(3) The image is as far behind the mirror as the object is in front.
(4) The line joining the image to the object is perpendicular to the mirror.

Question 8.
(a) State three characteristics of the medium required for the propagation of sound waves.
(b) A source is producing 1200 sound waves in 3 seconds. If the distance covered by a compression and an adjacent rarefaction is 80 cm, find :
(i) Frequency, (ii) Wavelength, (iii) Velocity of sound wave.
(c) What do you mean by: (i) Wavelength, (ii) Frequency, (iii) Time period and (iv) Amplitude of a sound wave.
Answer:
(a) Waves can be produced in a medium if it possesses the following properties :
(1) It should be elastic in nature, so that it has the tendency to come back to the original position.
(2) It should have a high density so that the disturbance is transferred easily.
(3) It should be free from frictional resistance.

(b) (i) Number of waves produced in 3 s = 1200
Number of waves produced in 1 s = \(\frac{1200}{3}\) = 400
∴ Frequency (f) = 400 Hz.
(ii) Wavelength = Distance covered by a compression and an adjacent rarefaction Wavelength,
X = 80 cm = 0.8 m.
(iii) Velocity, ν=f x λ = 400 x 0.8 = 320 ms^-1.

(c) (i) Wavelength is defined as the linear distance between two consecutive compressions or two consecutive rarefactions.
(ii) The number of compressions or rarefactions taken together passing through a point in one second is called frequency.
(iii) Time period is defined as the time taken by two consecutive compressions or rarefactions to cross a point.
(iv) Amplitude is defined as the magnitude of maximum displacement of a vibrating particle about its mean position.

Question 9.
(a) Two conductors A and B are joined by a copper wire. State the direction of flow of electrons in each of the following cases :
(i) If A is negatively charged and B is uncharged.
(ii) If A is negatively charged and B is positively charged.
(iii) If A is positively charged and B is negatively charged.
(b) What are insulators and conductors of electricity ? Give two examples of each.
(c) Draw a simple electric circuit consisting of a battery, a key, a rheostat, a lamp, an ammeter and a voltmeter.
Answer:
(a) (i) From A to B, (ii) From A to B, (iii) From B to A.
(b) The substances which do not allow the current to flow through them are called insulators.
For example, rubber and plastic.
The substance which allow current to flow through them easily are called conductors.
For example, all metals such as copper, aluminium etc.

Question 10.
(a) (i) Define 1 volt potential difference.
(ii) Calculate the potential difference across the ends of a wire of resistance 3Q when a current 2.5 A passes through it.
(b) State three ways to save energy.
(c) State four properties of magnetic field lines.
Answer:
(a) (i) Potential difference between two points is said to be 1 volt if work done in transferring 1 coulomb of charge from one point to the other point is 1 joule.

(ii) Given : R = 3Ω, I = 2.5 A From Ohm’s law,
V = IR
∴ Potential difference, V = 2.5 x 3 = 7.5 V.

(b) Energy can be saved by following ways :
(1) The use of compact fluorescent lights (CFL) saves energy and they may last 6 to 10 times longer than the incandescent lights.
(2) The use of LED (light emitting diode) bulbs for lighting reduces the consumption of energy. It also helps in reducing global warming.
(3) By properly insulating a home, it is possible to maintain a comfortable temperature inside. It will reduce the cost of heating devices in winter and cooling devices in summer.

(c) The magnetic field lines have the following properties :
(1) They are closed and continuous curves.
(2) The tangent at any point on a field line gives the direction of magnetic field at that point.
(3) They never intersect one another.
(4) They are crowded near the poles of the magnet where the magnetic field is strong.

ICSE Class 9 Physics Question Papers with Answers

ICSE Class 9 Physics Sample Question Paper 6 with Answers

Section -1
(Attempt all questions from this section)

Question 1.
(a) A screw gauge has pitch of 1.0 mm and 200 divisions on the circular scale. Will it be possible to increase the accuracy of the gauge arbitrarily by increasing the number of divisions on the circular scale ?

(b) Fill in the blanks :
(i) Zero error is positive when the zero of vernier scale lies to the of the zero of the main scale, when the two jaws of the vernier are in contact.
(ii) Zero error is negative when the zero of vernier scale lies to the of the
zero of the main scale, when the two jaws of the vernier are in contact.

(c) Can a body have constant speed and still be accelerating ?

(d) Two similar vehicles are moving with same velocity on the road, such that one of them is loaded and the other is empty. Which of the two vehicles will require larger force to stop ?

(e) If the earth attracts an apple, does the apple also attract the earth ? If so, why does the earth not move towards the apple ?
Answer:
Number of divisions on the circular scale \(\text { Least Count }=\frac{\text { Pitch }}{\text { Number of divisions on the circular scale }}\)
Hence, on increasing the number of divisions on the circular scale, the least count of the gauge decreases, i.e., accuracy of gauge can be increased by increasing the number of divisions on circular scale.

(b) (i) Right
(ii) Left

(c) Yes, a body can have constant speed and still be accelerating. When the body moves along a circular path with uniform speed, it possesses centripetal acceleration.

(d) A larger force is required to stop the loaded vehicle than the empty one. This is because the loaded vehicle has a greater momemtum than the empty vehicle as the mass of the loaded vehicle is more than that of the empty vehicle. Thus, it requires a greater force to stop.

(e) Yes, the apple attracts the earth with the same force with which the earth attracts the apple. Due to the large mass of the earth, the acceleration produced in it is negligible, and goes unnoticed. Hence, the earth does not seem to move towards the apple.

Question 2.
(a) Why do the bodies of deep sea fishes burst on bringing them above the sea level ?
(b) Why does a ship sink to a greater depth in river water than in sea water ?
(c) State two uses of biogas.
(d) Name the S.I. unit of heat and how is it related to the unit calorie ?
(e) A jar has water with 25 cm of height. Find the pressure of water at the bottom of the jar, ignore the atmospheric pressure and use the acceleration due to gravity g = 10 ms^-2, and the density of water 1000 kg m^-3.
Answer:
(a) The pressure in the lower levels of sea is a lot greater than the atmospheric pressure. To thrive in such high pressure, the blood of deep sea fishes contains dissolved oxygen at a very high pressure as compared to atmospheric pressure. Thus, when the fishes are brought to sea level, the difference in pressure of oxygen within their bodies and atmosphere bursts open their bodies.

(b) The density of sea water, because of the presence of impurities like salt etc., is greater than that of river water. Therefore, a lesser volume of the ship will be immersed in sea water to balance its weight and hence, the ships sinks to greater depths in river water.

(c) Two uses of biogas are as follows :
(i) Biogas is used for cooking food.
(ii) Biogas is being used for street-lighting.
(iii) The S.I. unit of heat is joule (J).

(d) 1 J = 0.24 cal (nearly).

(e) Given : h = 25 cm = 0.25 m, g = 10 ms^-2, ρ = 1000 kg m^-3
Using P = hρg
P = 0.25 x 1000 x 10
Pa = 2500 Pa

Question 3.
(a) A ray of light XY is incident on a mirror as shown in the figure. The angle of incidence for this ray is the angle between it and the line joining one of the two other points in the figure. Name these two points and show the course of rays after reflection.

(b) You have a spherical mirror. The image of an object placed in front of the mirror is virtual. If the position of the object is changed, the image remains virtual and erect. Is the spherical mirror concave or convex ? Give reason.
(c) For driving a car what type of mirror would you prefer to see the traffic at your back and why ?
(d) Complete the following sentence :
(e) A plane mirror produces a………………………… and an…………………. image.
(f) In case of a convex mirror, if the object is moved away from the surface of the mirror, how does the position and size of the image change ?
Answer:
(a) The angle of incidence is the angle between the incident ray and the normal at the point of incidence. A line joining the centre of curvature and the point of incidence is a normal at the point of incidence. Thus, the given two points are C and Y and the course of the rays is shown in the given figure.
C and F are respectively centre of curvature and focus.

(b) A convex mirror always produces a virtual and erect image irrespective of the position of the object in front of the mirror. So the given spherical mirror is convex in nature.

(c) We prefer a convex mirror for observing the traffic behind us because its field of view is much larger than the plane mirror.

(d) Virtual; erect

(e) As the object is moved away from a convex mirror, the distance of the virtual image formed behind it, from the mirror, increases (between pole and focus), i.e., the image shifts from the pole towards the focus and the size of the image gradually decreases. When the object is at infinity, the image is at its focus.

Question 4.
(a) You are given a primary and a secondary cell of the same e.m.f. From which cell, will you be able to draw a larger current and why ?
(b) Fill in the blanks :
(i) A source of direct current or e.m.f. is an arrangement which can bring about the of free electrons in a conductor in a particular direction.
(ii) An eletrochemical cell or cell is an arrangement which converts………………………. into electrical energy.
(c) Give four examples of primary cells.
(d) What are natural magnets ? Give example.
(e) Define magnetic equator.
Answer:
(a) The internal resistance of a secondary cell is less than that of a primary cell and more current flows when resistance is less. So, the secondary cell will provide a greater amount of current.
(b) (i) Motion,
(ii) Chemical energy
(c) Examples of primary cells are – (1) Simple voltaic cell, (2) Daniel cell, (3) Leclanche cell, (4) Dry cell.
(d) The natural magnets are the ones which occur naturally in nature. For example, lodestone.
(e) The line joining the points on the earth where a magnetic needle points horizontally is called the magnetic equator.

Section- II
(Attempt any four questions from this section)

Question 5.
(a) State the difference between speed and velocity.
(b) Mention three uses of velocity time graphs.
(c) How is the time period of a simple pendulum affected in the following situations :
(i) Amplitude of the pendulum is increased.
(ii) The length of the pendulum is doubled.
(iii) The brass bob is replaced with an identical aluminium bob.
(iv) The value of g is made one-fourth.
Answer:
(a) Speed is the rate of change of distance. It is a scalar quantity and is always positive. Velocity is the rate of change of displacement. It is a vector quantity and can be positive, negative or zero.

(b) Velocity-time graphs have the following uses :
(1) To determine the total distance travelled by a particle.
(2) To determine instantaneous velocity of the particle.
(3) To determine the acceleration of the object.

(c) The time period of a pendulum is given by the expression \(\mathrm{T}=2 \pi \sqrt{\frac{\mathrm{L}}{g}}\)
(i) The time period of a pendulum does not depend upon its amplitude, hence there is no change.
(ii) The time period of a pendulum is directly proportional to the square root of its length. When length is increased, the time period will also increase. Hence, when the effective length is doubled, time period increases times.
(iii) The time period of a pendulum does not depend upon its amplitude, hence there is no change.
(iv) The time period of a pendulum is directly proportional to the square root of its length. When length is increased, the time period will also increase. Hence, when the effective length is doubled, time period increases times.

Question 6.
(a) State three factors that prevents us in making use of solar cell panels to meet all our domestic needs.
(b) State three steps that can help in reducing global warming.
(c) State the weather forecast in the following situations :
(i) Air is humid and barometer pressure falls suddenly.
(ii) Barometric pressure rises steeply.
(iii) Barometric pressure does not change.
(iv) Barometric pressure falls gradually over a number of days.
Answer:
(a) The following factors prevent the use of solar cell panels to meet all our domestic needs of electricity :
(1) High cost of installation.
(2) Limited availability of special grade silicon to make solar cells.
(3) The effective energy obtained is not always constant and changes will seasons.

(b) Steps to reduce global warming are :
(i) By replacing a regular incandescent light bulb with a compact fluorescent light bulb (CFL) or LED.
(ii) By choosing energy efficient appliances when making new purchases. By using the washing machine or dishwasher only when they are full.

(c) (i) The forecast is rain storm.
(ii) The forecast is dry weather with strong anticyclonic winds.
(iii) The forecast is fair weather.
(iv) The forecast is that weather gradually changes from fair to windy over a number of days.

Question 7.
(a) How will you distinguish, without touching, between a plane mirror, concave mirror and a convex mirror ?(b) Define the following :
(i) Pole or vertex
(ii) Centre of curvature
(iii) Radius of curvature
(c) An object is placed in front of a concave mirror of radius of curvature 16 cm at a distance of (i) 10 cm and (ii) 5 cm. Find the position and nature of the image in each case.
Answer:
(a) To distinguish between a plane mirror, a convex mirror and a concave mirror, the given mirror is held near the face and the image is seen.
(1) If the image is upright, of same size as the object and it does not change in size when the mirror is moved then the mirror is a plane mirror.
(2) If the image is upright, magnified and becomes inverted when the mirror is moved away from the face then the mirror is a concave mirror.
(3) If the image is upright, diminished and remains upright when the mirror is moved away from the face then the mirror is a convex mirror.

(b) (i) The central point of a mirror is called its pole or vertex (P).
(ii) The centre of the sphere of which the mirror is a part is called the centre of curvature.
(iii) The radius of the sphere of which the mirror is a part is called the radius of curvature.

Question 8.
(a) Establish the relationship between speed of sound, its wavelength and frequency. If velocity of sound in air is 340 ms^-1 calculate
(i) Wavelength when frequency is 2000 Hz,
(ii) Frequency when wavelength is 1.7 m.
(b) A sound wave travels at a speed of 330 ms^-1. If its wavelength is 1.5 cm, what is the frequency of the wave ? Will it be audible ?
(c) Draw a curve showing density or pressure variations with respect to distance for a disturbance produced by sound. Mark the position of compression and rarefaction of this curve. Also define wavelengths and time period using this curve.
Answer:
(a) The speed of sound is defined as the distance which a point on a wave, such as a compression or a rarefaction, travels per unit time.
We Know that

Here, λ, is the wavelength of the sound wave. It is the distance travelled by the sound wave in one time period (T) of the wave. Thus,
v = λf
Hence, Speed = Wavelength x Frequency

The sound will not be audible as human beings can hear only upto 20000 Hz.

(c) The curve is as shown in the figure. Wavelength is defined as the distance between two successive compressions or two successive rarefactions. Time period is defined as the time taken by the disturbance to travel between two successive compressions or between two successive rarefactions.

Here C denote compression and R denote rarefaction. The distance between two compressions is AB, the wavelength and the time taken to travel distance AB is the time period.

Question 9.
(a) (i) What is a primary cell ?
(ii) State two advantages of primary cell over a secondary cell.

(b) A conductor carries a current of 0.2 A.
(i) Find the amount of charge that will pass through the cross-section of conductor in 30 s.
(ii) How many electrons will flow in this time interval if charge on one electron is 1.6 x 10^-19 c
(iii) Consider two spheres A and B, one positively charged and the other negatively charged respectively.

(c) These spheres are placed in contact. Answer the following :
(i) Which sphere is at a higher potential ?
(ii) Which sphere is at a lower potential ?
(iii) In which direction will the convectional current flow ?
(iv) In which direction will the electronic current flow ?
Answer:
(a) (i) Primary cell is an electrochemical cell which cannot be recharged, but the chemicals have to be replaced after a long use. The reactions taking place in the cell are irreversible.
(ii) Advantages of primary cell over a secondary cell are :
(1) A primary cell starts working immediately after its construction whereas a secondary cell has to be charged first so as to obtain electrical energy from it, i.e., it requires a lot of time before it can be put to use.
(2) The initial cost of a primary cell is cheaper than that of a secondary cell.

(b) Given : I = 0.2 A, t = 30 s
(i) Charge = Current x Time
or Q = I x t = 0.2 x 30 = 6 C

(ii) If ‘n’ electrons flow and ‘e’ is the charge on one electron, then total charge passed is
Q = ne
\(n=\frac{Q}{e}=\frac{6}{1.6 \times 10^{-19}}=3.75 \times 10^{19}\)

(c) (i) The positively charged sphere is at a higher potential.
(ii) The negatively charged sphere is at a lower potential.
(iii) Conventional current flows from shpere A to sphere B.
(iv) Electronic current flows from sphere B to sphere A.

Question 10.
(a) What is a neutral point ? State the positions of neutral points when a magnet is placed with its axis in the magnetic meridian and with its north pole (i) pointing towards the geographic north, (ii) pointing towards the geographic south.
(b) (i) Define current.
(ii) Calculate the current flowing through a wire of resistance 6 Q connected to a battery of potential difference 1.5 V.
(c) State four differences between electromagnet and permanent magnet.
Answer:
(a) Neutral point is a point where the magnetic field of a magnet is equal in magnitude to the earth’s horizontal magnetic field, but it is in opposite direction. Thus, the resultant (or net) magnetic field at the neutral points is zero.
(i) In east-west direction,
(ii) In north-south direction.

(b) (i) Current is the rate of flow of charge across a cross-section normal to the direction of flow of current.
(ii) Given : R = 6 Ω, V= 1.5 V
From Ohm’s law,
V = IR
Current in wire, \(\mathrm{I}=\frac{\mathrm{V}}{\mathrm{R}}=\frac{1.5}{6}=0.25 \mathrm{~A}\)

(c)

Electromagnet	Permanent Magnet
It is made of soft iron.	It is made of steel.
The magnetic field strength can be changed.	The magnetic field strength cannot be changed.
The polarity of an electromagnet can be reversed.	The polarity of a permanent magnet cannot be reversed.
It can easily be demagnetised by switching off the current.	It cannot be easily demagnetised.

ICSE Class 9 Physics Question Papers with Answers

ICSE Class 9 Physics Sample Question Paper 5 with Answers

Section-1
(Attempt all questions from this section)

Question 1.
(a) How will you express the result of a measurement of a physical quantity ?
(b) What do you mean by the following terms :
(i) Least count of an instrument
(ii) Vernier constant ?
(c) State the parameters on which time period of a simple pendulum does not depend.
(d) A vernier scale has 50 divisions which coincide with 49 divisions of the main scale. The main scale is graduated in 1/2 mm steps. What is the least count of the vernier ?
(e) Calculate the length of a second’s pendulum at a place where acceleration due to gravity is 9.8 m/s².
Answer:
(a) Result of a measurement of a physical quantity is expressed by a number of numerical measure accompanied by a unit. Thus, measurement of a physical quantity (Q) = Numerical measure (n) x unit (μ)

(b) (i) Least count of an instrument means the least or smallest measurement which can be measured by the instrument accurately.
(ii) Vernier constant is equal to the difference between the values of one main scale division and one vernier scale division.

(c) The period of oscillation does not depend on :
(1) mass of the material and shape of the bob
(2) amplitude of oscillation.
Answer:
(a) Result of a measurement of a physical quantity is expressed by a number of numerical measure accompanied by a unit. Thus, measurement of a physical quantity (Q) = Numerical measure (n) x unit (u)

(b) (i) Least count of an instrument means the least or smallest measurement which can be measured by the instrument accurately.
(ii) Vernier constant is equal to the difference between the values of one main scale division and one vernier scale division.

(c) The period of oscillation does not depend on :
(1) mass of the material and shape of the bob
(2) amplitude of oscillation.

Question 2.
(a) An insect is crawling on a cycle rim of radius r. What will be the distance and displacement of the insect
(i) in half revolution, and
(ii) in one complete revolution?
(b) Fill in the blanks :
(i) The velocity-time graph of a particle in uniform motion is a straight line ………… to the time axis.
(ii) The time-distance graph of a particle in uniform motion is a straight line ………… to the time axis.
(c) Sketch the velocity-time graph for an object moving with
(i) uniform velocity
(ii) uniform acceleration.
(d) Comment on the type of motion represented by the displacement-time graph shown in the given figure. What conclusions can we draw from this graph ?

(e) A particle moves 8 m due east and then through 6 m due north.
(i) How much is the net distance moved ?
(ii) What is the magnitude of the net displacement ?
Answer:
(a) (i) In half revolution, distance travelled by the insect will be equal to the circumference of the half circular rim, i.e., nr and displacement will be the shortest distance between initial and final positions, i.e., 2r.

(ii) In complete revolution, distance travelled by the insect will be the circumference of the rim, 2nr and displacement will be zero.

(b) (i) Parallel
(ii) Inclined

(c) (i) For uniform velocity
(ii) For uniform acceleration

(d) The particle here moves with a uniform velocity from t = 0 to t = 2s represented by an inclined line. Then the line becomes parallel showing no displacement. Therefore, it remains at rest.
The slope of the graph from f = 0tof = 2sis given by :
\(\text { Slope }=\frac{10-0}{2-0}=5\)
This represents the velocity of the particle. Thus, the particle has a uniform velocity of 5 ms^-1 from t = 0 to t = 2 s. After that the particle remains at rest.

(e) The particle starts from 0. It moves through 8 m due east to reach A and then through 5 m due north to reach B.
(i) Total distance moved is8m + 6m = 14m
(ii) Magnitude of the net displacement is OB

Question 3.
(a) Why does a long jump runner come running before taking a leap ?
(b) Why are dams made very broad at the base ?
(c) What would be the difference in weight, in any, of one kilogram of cotton and one kilogram of iron, if both are weighed in vacuum ?
(d) What is the function of the gravity bulb in a hydrometer ?
(e) The portion of a wooden block, floating inside water, measures 50 cm x 50 cm x 50 cm. Find the magnitude of the buoyant force acting on the block.
Answer:
(a) By running, the runner’s body acquires an ‘inertia of motion’ which tends to keep the runner moving forward. He therefore, achieves a longer jump compared to what he would have got had he taken a jump from a standing ‘at rest’ position.

(b) The use of broad base in dams decreases the pressure of the weight of water on the base. This helps the base, and hence the dam built on it, to stay intact.

(c) There would be no difference in the weights of cotton and iron in vacuum. This is because, in vacuum, there is no upthrust at all on any object. Thus, objects of equal mass, irrespective of their volume, have equal weight in vacuum.

(d) The gravity bulb of a hydrometer is loaded with iron balls or pitch. This results in a lowering of the C.G. of the hydrometer as a whole. This lowering of the C.G. in turn helps the hydrometer to float in a stable, upright position when it is immersed in a liquid.

(e) The buoyant force = Weight of water displaced
= Volume of water displaced x Density of water x g
= (50 x 50 x 50 x 10^-5 m³) x (1000 kg/m³) x 9.8 ms^-2
= 125 x 9.8 kg ms^-2
= 1225 N.

Question 4.
(a) Name four green house gases.
(b) Deep pond of water has its top layer frozen during winter. State the expected temperature of water layer (i) just in contact with ice, and (ii) at the bottom of the pond.
(c) What is the number of images formed when an object is placed between two parallel plane mirrors ? Why do the distant images appear fainter ?
(d) The speed of propagation of sound waves, in a gaseous medium equals 340 ms^-1. If the frequency of these waves is 1700 Hz, find the wavelength.
(e) The upper blood pressure of a patient is 150 cm of Hg whereas the normal pressure should be 120 cm of Hg. Calculate the extra pressure generated by the heart in S.I. unit. Take density of Hg = 13600 kg m^-3 and g =8 ms^-2.
Answer:
(a) The names of four green house gases are carbon dioxide, water vapours, methane and
chlorofluorocarb ons.

(b) (i) The temperature of water just in contact with ice is 0°C.
(ii) The temperature of water at the bottom of the pond whose top layer has frozen is 4°C.

(c) The number of images formed will be infinite except when the object is placed exactly midway between the two mirrors. In that case, only two images will be produced.
The distant images appear fainter because they are formed through repeated reflections and some of the incident light energy gets lost at each reflection.

(e) Given : ρ = 13600 kg m^-3, g = 9.8 ms^-2
Extra pressure = 150 – 120 = 30 cm = 0.3 m of Hg
From relation  P = ρgh
Extra pressure, P = 0.3 x 13600 x 9.8
= 3.9984 x 10⁴ Pa.

Section – II
(Attempt any four questions from this section)

Question 5.
(a) Name the instrument you would use to measure the following :
(i) Thickness of a thin glass plate
(ii) Thickness of a paper
(iii) Internal diameter of a test-tube.

(b) The pitch of a screw is 0.1 cm. Find the reading of the screw gauge shown in the given figure.

(c) A simple pendulum is set up in a laboratory at the sea level. How would its time period change if it is shifted to :
(i) The moon,
(ii) a deep mine,
(iii) a place at Mount Everest
(iv) an artificial satellite on earth?
Answer:
(a) (i) Micrometer screw gauge
(ii) Micrometer screw gauge
(iii) Vernier callipers

(b) \(\frac{\text { Pitch }}{\text { Number of divisions on circular scale }}\)
\(\frac{0.1}{100}\) = 0.001cm
Reading of the screw gauge = MSR + CSD x LC
= 0.6 cm + 93 x 0.001 cm
= 0.6 + 0.093 = 0.693 cm.

(c) (i) Time period increases = \(\left(\text { as } \mathrm{T} \propto \frac{1}{\sqrt{g}}\right)\)
(ii) Time period increases = \(\left(\text { as } \mathrm{T} \propto \frac{1}{\sqrt{g}}\right)\)
(iii) Time period increases as on a mountain, acceleration due to gravity decreases and  \(\mathrm{T} \propto \frac{1}{\sqrt{g}}\)
(iv) Time period becomes infinite, as in an artificial satellite, there is zero gravity and \(\mathrm{T} \propto \frac{1}{\sqrt{g}}\)

Question 6.
(a) A body P has a mass of 20 kg and is moving with a velocity of 5 m/s. Another body, Q has a mass of 5 kg and is moving with a Velocity of 20 m/s. Calculate the ratio of the momentum of P and
(b) What force would be required to accelerate a body of mass 20 kg from 1.5 ms^-1 to 9 ms^-1 in one-third of a minute ?
(c) In the given figure, the displacement of an object is shown at different times. Calculate the speed of the object as it moves for 0 s to 5 s, 5 s to 7 s, 7 s and 9 s. Also, calculate the average velocity during the time interval 5 s to 9 s.

Answer:
(a) For body P,
Given : m = 20 kg, ν = 20 m/s
∴ Momentum of the body P = 20 kg x 5 m/s = 100 kg m/s.
For body Q,
Given : m = 5 kg, ν = 20 m/s
∴ Momentum of the body Q = 5 kg x 20 m/s = 100 kg m/s
\(\frac{\text { Momentum of body } \mathrm{P}}{\text { Momentum of body } \mathrm{Q}}=\frac{100}{100}=\frac{1}{1} \text { or } 1: 1\)

Question 7.
(a) (i) Define pressure and give its S.I. unit.
(ii) The pressure in a water pipe on the ground floor of a building is 100000 Pa. What is the pressure in a water pipe on the first floor at a height of 2.5 m ? (Density of water = 1000 kg m^-3, g = 10 ms^-2)

(b) A given solid weighs 0.100 kgf in air, 0.080 kgf in a liquid and 0.075 kgf in water. What is : (i) the apparent loss of weight of the solid in liquid, (ii) the apparent loss of weight of the solid in water and (iii) the R.D. of the liquid ?

(c) A block of wood of density 0.8 x 10³ kg/m³ just begins to sink when a mass of 1.6 kg is placed on it. What is the volume of the block ?
Answer:
(i) The pressure at a given point is the (normal) force acting there per unit area. The
S.I. unit of pressure is Nm^-2 or pascal (Pa).

(ii) We have,
Pressure on ground floor = Pressure on first floor + Pressure due to a water column of height 2.5 m
100000 Pa = Pressure on first floor + (2.5 x 1000 x 10) Pa
∴ Pressure on first floor = 100000 – (2.5 x 1000 x 10) Pa
= 75000 Pa

(b) (i) Apparent loss of weight of the solid in liquid = (0.100 – 0.080) kgf = 0.020 kgf
(ii) Apparent loss of weight of the solid in water = (0.100 – 0.075) kgf = 0.025 kgf
\(\text { R.D. of liquid }=\frac{\text { Loss of weight in liquid }}{\text { Loss of weight in water }}=\frac{0.020}{0.025}=0.8\)

(c) Under given condition
Weight of water displaced = Weight of the block + Weight placed on the block and, Volume of water displaced = Volume of the block.
Let the volume of the block be V m³.
Then, Mass of water displaced = (V) x (1000)[∵ Density of water = 1000 kg/m³]
∴ Weight of water displaced, W₃ = V x 1000 x 9.8
Mass of block = V x ρ                                 [ρ = density of block]
∴ Weight of block, W₁ = V x ρ x g
= V x 0.8 x 10³ x 9.8
weight placed on the block W₂ = 1.6 x 9.8
∴ W₁ + W₂ = V x 0.8 x 10³ x 9.8 + 1.6 x 9.8
Dividing both sides by 9.8 ms^-2 and on solving, we get
1000 V = 800 V + 1.6
or  (1000 – 800) V = 1.6 kg
\(\mathrm{V}=\frac{1.6}{200}\) = 8 × 10^-3 m³

Question 8.
(a) The given diagram shows an object PQ placed in front of a plane mirror. Complete the ray diagram to show the formation of image by the plane mirror of the object PQ.

(b) The angle between an incident ray and the mirror is θ as shown in the given figure. The total angle turned by the ray is 80°. What is the value of θ ?

(c) The diagram below shows a point object P in front of a plane mirror MN.
(i) Complete the diagram by taking two rays from the point P to show the formation of its image.
(ii) Is the image formed real or virtual ? Explain why.

Answer:
(a) The completed ray diagram is as follows :

(b) The ray diagram is redrawn as shown below :

Since, Angle of incidence = Angle of reflection
Therefore, 9 = (90 – 40)° = 50°.

(c) (i) The ray diagram is as follows :

(ii) The image formed is virtual because the reflected rays seem to meet behind the mirror.

Question 9.
(a) (i) The frequency of a source of sound is 100 Hz. How many times does it vibrate in a minute ?
(ii) People living near the railway tracks often press their ears against the track to find whether a train in coming or not. Why ?

(b) Answer the following :
(i) What causes sound ?
(ii) Can sound travel in vacuum ?
(iii) How does the speed of sound differ in different media ?

(c) The speed of sound in air is 340 ms^-1 and in water is 1450 ms^-1. It takes 2 s for sound to reach a certain distance from the source placed in air.
(i) Find the distance.
(ii) How much time will it take for sound to reach the same distance when the source is in water ?
Answer:
(i) Number of vibrations produced in 1 s = 100
∴ Number of vibrations produced in 60 s = 100 x 60 = 6000

(iii) The reason is that the vibrations produced by the moving wheels of the train travel much faster through the steel track than through the air. So, the sound is heard through the track much before it is heard through the air. Thus, the person gets an indication of the coming of the train.

b(i) Sound is caused due to vibrations of a body.
(ii) No, sound cannot travel in vacuum.
(iii) Speed of sound is maximum in solids, less in liquids and least in gases.

(c) (i) Given : In air, v = 340 ms^-1, t – 2 s
From relation, \(v=\frac{d}{t}\)
Distance travelled by sound in air,
d = ν x t = 340 x 2 = 680 m.
ν = 1450 ms^-1, d = 680 m

(ii) In water,
∴ Time taken by sound to travel the distance ‘d’ in water will be
\(t=\frac{d}{v}=\frac{680}{1450}=0.47 \mathrm{~s}\)

Question 10.
(a) The figure shows a coil wound around a soft iron bar XY.
(i) State the polarity at the ends X and Y as the switch is pressed.
(ii) Suggest one way of increasing the strength of electromagnet so formed.

(b) A coil of insulated copper wire is wound around a piece of soft iron and current is passed in the coil from a battery.
(i) What name is given to the device so obtained?
(ii) Give two uses of the device mentioned by you.

(c) Name the physical quantities having the following S.I. units :
(i) volt
(ii) coulomb
(iii) ohm and
(iv) ampere.
Answer:
(a) (i) X is north pole, Y is the south pole.
(ii) The strength of the electromagnet can be increased by increasing the current in the coil.

(b) (i) The device obtained is an electromagnet.
(ii) An electromagnet can be used for the following purposes :
(1) For removing pieces of iron from wounds.
(2) In electrical devices like bell, telegraph, etc.

(c) (i) Potential difference
(ii) Charge

ICSE Class 9 Physics Question Papers with Answers

ICSE Class 9 Physics Sample Question Paper 4 with Answers

Section-1
(Attempt all questions from this section)

Question 1.
(a) What do you understand by (i) amplitude and (ii) frequency of oscillation of a simple pendulum ?
(b) Draw a graph of l, the length of a simple pendulum, against T², the square of its time period.
(c) Is a month equal to a lunar month ? Give reason.
(f) The iron bob of a given pendulum is replaced by a lead one of the same radius. Lead is known to be denser than iron. What would be the effect of this change on the pendulum’s time period ?
(g) An astronaut carries a second’s pendulum to the moon where the gravity is only 1/9th of that of the earth. What will be the time period of the pendulum there ?
Answer:
(a) (i) The amplitude of a simple pendulum is the maximum displacement of its bob from its equilibrium or mean position.
(ii) The frequency of oscillation of simple pendulum equals the number of complete oscillation made by it in one second.

(b) The required graph is a straight line, e., T² α l.

(c) No, the month is defined in terms of the motion of the earth round the sun while the lunar month is defined in terms of the motion of the moon round the earth.

(d) Since the lead bob is of the same radius as the iron one, there is no change in the length of the pendulum. As time period is independent of the mass of the bob, there would be no effect on the time period of the pendulum.

(e) We have

Question 2.
(a) What physical quantity is represented by the symbol ‘g’ ? What is its meaning ?
(b) Fill in the blanks :
(c) The physical quantity representing rate of change of displacement is known as ………………………….
(d) The motion of a body for which the acceleration is zero is known as……………………….
(g) The electrons in a T.V. tube travel a distance of 0.2 m, at a constant speed, in 10^-5 What is their average speed ?
(h) Comment on the type of motion represented by the velocity-time graph shown in the figure. What conclusion can you draw from this graph ?

(e) Rhea takes 15 minutes to go from her home to school and 20 minutes for her return journey. If the distance between the school and the home is 3.5 km, what is her (i) average speed, (ii) average velocity?
Answer:
(a) The symbol ‘g’ represents the acceleration due to gravity. It is the value of acceleration, with which all freely falling objects fall towards the earth. The value of ‘g’ is nearly 9.8 ms^-2 or nearly 980 cm s^-2.

(b) (i) Velocity
(ii) Uniform motion.

(c) We know,
\(\text { Average speed }(v)=\frac{\text { Total distance travelled }}{\text { Total time taken }}\)
Here, distance travelled= 0.2 m, time taken = 10^-5 s.
\(v=\frac{0.2}{10^{-5}}=2 \times 10^{4} \mathrm{~m} / \mathrm{s}\)

(d) The particle, in this case, remains at rest (v – 0) from t = 0 to t = 2. After that, it has a uniformly accelerated motion.
The slope of the graph \(=\frac{30-0}{6-2}=\frac{30}{4}=7.5\)
This slope represents the acceleration. We can, therefore, conclude that the particle moves with a uniform acceleration of 7.5 ms^-2 from f = 2s to f = 6s.

(e) (i)

(ii)

The total displacement is zero because the starting and end points of the displacement of Rhea are the same (she is back home).

Question 3.
(a) A girl running on the ground, trips on a stone. What is likely to happen to her and why?
(b) The foundations of a high rise building are made very wide. Why?
(c) Will one kilogram of feather weigh the same in a vacuum as it does in air?
(d) Two spherical balls, of the. same radius V are made out of copper and iron. If these balls are completely dipped inside a given liquid, what can we say about the Toss in weight’ suffered by them?
(e) An object weighs 70 kg in air. It displaces 2000 cm³ of water when fully immersed under water. Find the relative density of the material of the object.
Answer:
(a) The girl is likely to fall forwards. This is because of inertia of motion. When she trips on a stone, her feet suddenly come to rest but the upper part of her body continues to move forward because of inertia of motion. She, therefore, falls forward.

(b) A high rise building will obviously have a much larger weight than a single or double storeyed building. The use of very wide foundations helps us to increase the area over which the weight of the building acts. This, in turn, reduces their pressure on the ground and prevents the building from sinking.

(c) No, in vacuum, there would be no upthrust or buoyant force acting on the feather. In air, however, there would be small upthrust. The weight of one kilogram of feather, in air, will therefore, be a little less than its weight in vacuum.

(d) The Toss in weight’ will be equal for both the balls. This is due to the fact, that both the balls are of the same volume. Hence, the upthrust (= loss in weight) experienced by them will also be the same.

(e) Volume of water displaced by the object = 2000 cm³
= 2000 x 10^-6 m³ = 2 x 10^-3 m³
∴ Weight of water displaced by the object = (2 x 10^-3) x 10³ = 2 kgf
∴ R.D. of the material of the object = \(\frac{70}{2}\) = 35

Question 4.
(a) What two policy measures must the government take to minimise global warming?
(b) State two properties of a medium on which the speed of sound in it depends.
(c) How will the letters of the word ‘POLEX’ be seen in a plane mirror held parallel to the plane of this paper?
(d) The speed of propagation of sound waves, in a gaseous medium equals 340 ms⁴. If the wavelength of these waves equals 17 cm, find their frequency.
(e) Draw a graph to show the variation in the volume of water with temperature in the temperature range from 0°C to 10°C.
Answer:
(a) The government must undertake the following two policy measures to minimise global warming :
(1) Educating children to live a sustainable lifestyle.
(2) Controlling population through family planning, welfare reforms and the empowerment of women.

(b) Speed of sound depends upon the following two properties of a medium :
(1) elasticity
(2) density.

(c) The word will get laterally inverted and would look like XHJOT.

(d) We have,
Speed = Frequency x Wavelength

(e) Variation in volume of water in range of temperature 0°C to 10°C

Section – II
(Attempt any four questions from this section)

Question 5.
(a) Express the (i) fermi, (ii) angstrom, and (iii) micron in metre.
(b) Name the instrument you would use to measure the following :
(i) diameter of a pin
(ii) diameter of a sphere
(iii) width of a box.
(c) The main scale of a given vernier callipers is caliberated in mm. 10 divisions of vernier scale are equal to 9 divisions of the main scale. Find its least count. When the diameter of a sphere is measured, the zero of vernier scale lies between 0 and 1.1 cm and the 8th division of the vernier scale coincides with the main scale. Find the diameter of the sphere.
Answer:
(i) 1 fermi (f) = 10^-15 m, (ii) 1 angstrom (A) = 10^_10m, (iii) 1 micron (p) = 10^-6
(i) Micrometer screw gauge, (ii) vernier callipers, (iii) meter scale.
Least count (LC) of given vernier calliper = \(\frac{x}{n}\)
= \(\frac{1}{10}\) = 0.1 mm = 0.01 cm 10
Diameter of the sphere = Main scale reading + VSD x LC
1.0 cm + 8 x 0.01 cm
= 1.08 cm.

Question 6.
(a) Obtain the relationship between S.I. and C.G.S. units of force.
(b) How long would a force of 30 N act on a body of mass 10 kg so that the body gains a velocity of 24 ms^-1
(c) The velocity-time graph of a body is shown in the figure. Find its average acceleration over each of the intervals OA, AB, BC and CD.

Answer:
(a) S.I. unit of force is newton (N) and C.G.S. unit is dyne.
1 N = 1 kg x 1 ms^-2
= 1000 g x 100 cm s^-2 [∵ 1 kg = 1000 g, 1m = 100 cm]
= 10⁵ g cm s^-2
∴ 1 N = 10⁵ dyne          [ ∵ 1g cm s^-2 = 1 dyne]

The slopes of OA and BC are zero each. Thus, the average acceleration has the following values :
(1) zero over the interval OA;
(2) 10 ms^-2 over interval AB;
(3) zero over interval BC; and
(4) -10 ms^-2 over interval CD. (Here, the body experiences retardation)

Question 7.
(a) (i) The mass of a rectangular block is 500 g. It has a base of length =10 cm and breadth = 5 cm. Calculate in S.I. unit, the average pressure exerted by the block on its base. Assume g = 10 m/s²
(ii) Should we regard the pressure at a point in a liquid as a scalar or a vector quantity?
(b) The density of the material of a solid is 5000 kg m³. Its weight in air is 0.5 kgf. What would be its apparent weight, when completely immersed in a liquid of density 8000 kg m³?
(c) Two-fifths of a cylindrical block of wood, of relative density 0.8, floats in a liquid. Calculate the density of liquid in S.I. units.
Answer:
(a) (i) Weight of the block = 5 kg x 10 ms^{– 2} = 5 N
Its base area = 10 x 5 cm² = 50 x 10^-4 m² = 5 x 10^-3 m²
Average pressure on the base =\(\frac{5}{5 \times 10^{-3}}=10^{3} \mathrm{Nm}^{-2}\)= 1000 pascal.
(ii) The pressure at a point in a liquid is a scalar quantity.

(b) We have, Volume of solid = \(\frac{\text { Mass }}{\text { Density }}=\frac{0.5}{5 \times 10^{3}}\)= 10^-4 m³
∴ Mass of liquid displaced by it = 8000 x 10^-4 kg = 0.8 kg
∴ Apparent weight = Weight of solid in air – Weight of liquid displaced by it
= (0.5 – 0.8) = – 0.3 kgf
The negative sign here implies that the upthrust on the solid, when fully immersed in a denser liquid is more than the weight of the solid. Its apparent weight, in this floating condition, will then be zero.

(c) Relative density of block of wood =\(=\frac{\text { Density of block }}{\text { Density of water }}\)
Density of block = R.D. of block x Density of water
= 0.3 x 1000 kg/m³ = 800 kg/m³.
Let the volume of block be ‘V’.
∴ Volume of liquid displaced = Volume of submerged part = \(\frac{2 \mathrm{~V}}{5}\)
∴  Let the density of the liquid be ‘ρ’
Mass of displaced liquid, \(m=\left(\frac{2}{5} \mathrm{~V}\right) \rho\)
Weight of displaced liquid = mg \(=\left(\frac{2}{5} \mathrm{~V}\right) \rho g\)
According to floatation law, this is the weight of the block.
Also, Weight of the block = mg
= (Volume x Density) g
=(V x 800 kg/m³)g

Question 8.
(a) The angle between an incident ray and mirror is 50°. (i) What is the angle of incidence? (ii) What is the angle of reflection? (iii) What is the total angle formed by the ray of light?
(b) In the given figure, name the kind of mirror and show it on the diagram. Complete the ray diagram and find the position of centre of curvature and focus of the mirror if A₁B₁ is the image of object AB.
(c) Two plane mirrors are arranged parallel and facing each other at some separation. How many images are formed for a point source kept in between them? Show the formation of images with the help of a ray diagram.

Answer:
(a) The ray diagram for the given situation is as shown below.

(i) Angle of incidence = 40°
(ii) Angle of reflection = 40°
(iii) Total angle formed by the ray of light = 80°

(b) The complete ray diagram is shown below and the mirror used is a convex mirror.

(c) The number of images formed is infinite and the ray diagram is shown below :

Question 9.
(a) (i) Why is sound wave called longitudinal wave ?
(ii) Will the sound be audible if the string is set into vibration on the surface of the moon ? Give reason for your answer.
(b) State three characteristics of the medium required for propagation of sound.
(c) Waves of time period 12 s have wave velocity 25 ms^-1.
Find : (i) The wavelength of these waves, (ii) The horizontal distance between a wave crest and its adjoining wave trough.
Answer:
(a)
(i) Sound wave is called longitudinal wave because the particles of the medium vibrate in the direction of the propagation of wave.
(ii) No, we will not hear any audible sound on the surface of the moon. This is because sound requires a medium to propagate, and there is no atmosphere on the surface of the moon. Thus, the sound will not be heard.

(b) The medium required for propagation of sound must possess the following three characteristics :
(1) The medium must be elastic.
(2) The medium must have inertia.
(3) The medium should be frictionless.

(c) Given : T = 12 s, v = 25 ms^-1
(i) From relation, υ =\(\frac{\lambda}{\mathrm{T}}\)
Wavelength of wave, λ = ν x T
= 25 × 12 = 300m

(ii) The distance between a wave crest and its adjoining wave through =\(\frac{\lambda}{2} \)
\(=\frac{1}{2} \times \lambda=\frac{1}{2} \times 300=150 \mathrm{~m}\)

Question 10.
(a) State three properties of a magnet.
(b) State three advantages of an electromagnet over a permanent magnet.
(c) State four properties of magnetic field lines.
Answer:
(a) Three properties of a magnet are :
(1) Attractive property
(2) Directive property
(3) Poles exist in pairs.

(b) An electromagnet has the following advantages over a permanent magnet:
(1) The polarity of an electromagnet can be reversed by reversing the direction of current in its solenoid.
(2) An electromagnet can produce a strong magnetic field.
(3) The strength of the magnetic field of an electromagnet can be easily changed by changing the current (or the number of turns) in its solenoid.

(c) Magnetic field lines must have the following four properties :
(1) They travel from the north to the south pole of a magnet outside the magnet and from south to the north inside the magnet.
(2) They are closed and continuous curves.
(3) The tangent drawn at any point of the magnetic lines of force represents the direction of the magnetic field at that point.
(4) Two magnetic fields do not intersect each other.

ICSE Class 9 Physics Question Papers with Answers

ICSE Class 9 Physics Sample Question Paper 2 with Answers

Section -1
(Attempt all questions from this section)

Question 1.
(a) Define the light year. Express it in metre.
(b) A student measures the length of a line with a (ordinary) meter scale and quotes his result as 15.78 cm. Is this result acceptable?
(c) Name the two factors on which the time period of a simple pendulum depends.
(d) Fill in the blanks :
(i) The S.I. unit of pressure is …………………..
(ii) The backlash error can be there in a …………………..
(e) The time periods of two simple pendulums are in the ratio 2:1. What will be the corresponding ratio of their lengths?
Answer:
(a) A light year is defined as the distance travelled by light, in vacuum, in a time span of one
1 light year = 9.46 x 10¹⁵ m

(b) No. the meter scale can measure lengths only up to 0.1 cm, i.e., only up to the first decimal place. Hence, he is not justified in quoting his result up to the second decimal place.

(c) The time period of a simple pendulum depends upon (1) its effective length (l), and (2) the acceleration due to gravity (g) at the place where the pendulum is oscillating.

(d) (i) Pascal (Pa)
(ii) Screw gauge.

(e) For a simple pendulum, we have

Thus, the lengths of the two pendulums are in the ratio 4:1.

Question 2.
(a) Draw a diagram to illustrate the motion of a body whose speed remains constant but the velocity continuously changes.
(b) Fill in the blanks :
(i) The acceleration of a body, in uniform motion, equals to ………………..
(ii) A body is said to have a ……………….. when its final velocity is less than its initial velocity.
(c) A body (initially at rest), while going down an inclined plane, has an acceleration of 2 cm/s². What will be its velocity 5 seconds after the start ?
(d) The displacement-time graph for a particle is as shown in the figure. Is its motion uniform or non-uniform ?

(e) A train, moving with a velocity of 20 ms^-1, comes to rest in 5 seconds when the brakes are applied. What is its retardation ?
Answer:
(a) When a body moves with a uniform speed in a circular path, its speed remains constant but its direction of motion (and hence its velocity) continually changes.

(b) (i) Zero.
(ii) Retardation

(c) We know,
v = u + at
Given : u = 0, a = 2 cm/s², t = 5 s
v = 0 + 2 x 5 = 10 cm/s = 0.1 m/s

(d) The motion of the particle is non-uniform. This is because the displacement-time graph is a (parabolic) curve. It is not a straight line as it should be for a uniform motion.

(e) Given: u = 20 ms^-1, v = 0, t = 5 s
υ = u + at
0 = 20 + a x 5, where ‘a’ is the acceleration
Thus \(a=\left(\frac{0-25}{5}\right)=-4 \mathrm{~ms}^{-2}\)
The retardation is 4 ms^-2.

Question 3.
(a) A pile of books is kept on a cardboard sheet on a table. If the cardboard sheet is suddenly withdrawn, what happens to the pile, and why?
(b) Tractors usually have very wide rear wheels. Why ?
(c) When balloons are filled with hydrogen, they are seen rising towards the ceiling. However, when they are filled through the mouth, they sink to the floor. Explain why this happens ?
(d) Why does an object appear lighter, when suspended in a liquid ?
(e) Consider an iceberg floating in fresh water. Find the fraction of volume of the iceberg which is below the water surface. (Given : density of ice = 917 kg m^-3, density of fresh water = 1000 kg m^-3.)
Answer:
(a) The pile of books will remain intact. This is because of “inertia of rest”. When the cardboard sheet is suddenly withdrawn, the books continue to remain at rest because of their inertia.

(b) Tractors are used in fields where the soil is quite soft. Thus, if they exert a large pressure on the ground, their wheels will sink into the soft soil. However, use of wide rear wheels will decrease the pressure of their weight on the ground. This helps them to move on soft soil without getting stuck.

(c) The balloons experience an upthrust due to the air in the room. The density of hydrogen is considerably lower than that of air. The upthrust on a balloon filled with hydrogen is, therefore, more than its own weight. The balloon is therefore, pushed up and is seen rising towards the ceiling.

The density of air exhaled by the mouth is more than the density of the room air because of the presence of a large amount of carbon dioxide in the exhaled air. The weight of balloon filled through the mouth is more than the upthrust on it. This balloon, therefore, sinks to the ground.-

(d) The object experiences an upthrust, or a buoyant force, when suspended in a liquid. Because of this, the net downward force on it becomes smaller. It, therefore, appears lighter.

(e) Let V be the volume of the iceberg, and v’ that of its part below the water surface. We then have,
Weight of iceberg = Upthrust due to displaced water
Or V x 917 x g = υ‘ x 1000 x g
\(\frac{v^{\prime}}{\mathrm{V}}=\frac{917}{1000}=0.917\)

Question 4.
(a) Fossil fuels are energy rich compounds of an element X which were originally made by the plants with the help of sun’s energy.
(i) Name the element X.
(ii) Name another element which is usually found in combination with X in fossil fuels.

(b) State two characteristics which a source of energy should have.
(c) What do we understand by the term ‘optical medium’ ? Give example.
(d) Thunder is heard 8 seconds after a lightning flash. Calculate the distance in which the lightning occured if the mean temperature of the air is 20°C, velocity of sound in air at 20°C is equal to 340 m/s.
(e) Distinguish between heat and temperature.
Answer:
(a) (i) Carbon
(ii) Hydrogen

(b) A source of energy must have the following characteristics :
(1) It should be capable of providing adequate useful energy.
(2) It should be convenient to use.

(c) Any medium through which light passes is referred as an optical medium. For example, glass, water, air etc.

(d) As the thunder is heard 8 s after the lightning flash, the distance sound travelled in this interval of
time is :
340 x 8 = 2720 m.
The lightning occurred at a distance of 2720 m.

(e)

	Heat	Temperature
	Heat is form of energy obtained due to random motion of mole­cules in a substance.	Temperature is a quantity which determines the direction of flow of heat on keeping the two bodies at different temperature in contact.
	The S.I. unit of heat is joule (J).	The S.I. unit of temperature is kelvin (K).

Section – II
(Attempt any four questions from this section)

Question 5.
(a) Which instrument would be preferable for measuring lengths to an accuracy of :
(i) 1 mm, (ii) 1 mm, and (iii) 0.01 mm ?

(b) (i) A girl is swinging on a swing in a sitting position. How will the period of the swing be affected if she stands up ?
(ii) The bob of an oscillating pendulum is made of ice. How will the time period change if the ice starts melting ?
(iii) Will a pendulum gain or lose time when taken to a mountain ?

(c) A screw gauge has a pitch of 0.5 mm and there are 100 divisions on its circular head. When it was used to measure the diameter of a wire, the main scale reading was 3 mm and the 45th division of the circular head was seen to be coincident with the reference line. The zero of its circular division was seen to be coincident with the zero of the main scale when the two jaws were put in contact. What is the diameter of the wire ?
Answer:
Answer:
(a) In each case, we would need an instrument whose least count equals the desired accuracy. Thus, the instruments needed are :

• a meter scale
• a vernier calliper, and
• a screw gauge.

(b)
(i) As a girl stands up, the centre of gravity of the swing is raised up, i.e.r the length 7′ of the system decreases. Hence, the time period \(\left(\mathrm{T}=2 \pi \sqrt{\frac{l}{g}}\right)\) decreases.
(ii) The time period will not be affected because it is independent of the mass of the bob.
(iii) When a pendulum is taken to a mountain-top, g will decrease. Thus, \(\mathrm{T}=2 \pi \sqrt{\frac{l}{g}}\) will U increase, i.e., the pendulum will take more time to complete one oscillation. In other words, it will lose time.

(c) We have, ‘zero error’ in the given screw gauge = nil.
Pitch 0.5
Least count \(=\frac{\text { Pitch }}{100}=\frac{0.5}{100}=0.0005 \mathrm{~cm}\)
∴ Diameter of wire = Main scale reading + Coincident circular scale division x Least count
= 0.3 cm + 45 x 0.0005 cm
= (0.3 + 0.0225) cm = 0.3225 cm.

Questions 6.
(a) Mention any three differences between the mass and weight of a body.

(b) Calculate the force exerted by the earth on the moon. Take the mass of the earth M_e = 6 x 10²⁴ kg and the mass of the moon M_m = 7.4 x 10²² The distance between the earth and the moon is 3.84 x 10⁵ km. Also, G = 6.7 x 10“¹¹ Nm²/kg².

(c) The table below shows the distance, in cm, travelled by objects A, B and C during each second :

Time	Distance (in cm) covered each second by A, B and C
	Object A (cm)	Object B (cm)	Object C (cm)
1st second	20	20	20
2nd second	20	36	60
3rd second	20	24	100
4th second	20	30	140
5th second	20	48	.180

(i) Select the object which is moving with constant speed. Give reason for your choice.
(ii) Select the object which is moving with a constant acceleration. What is the value of this acceleration ?
(iii) Select the object which is moving with a variable acceleration.
(iv) Find how much distance each of the objects A, B and C cover in 5 seconds.
Answer:

Mass	Weight
1. The mass is the quantity of matter contained in a body. 2. Mass of a body is a scalar quantity 3. Its S.l. unit is kilogram (kg).	1. Weight is the force with which a body is attracted towards the centre of the earth. 2. Weight of a body is a vector quantity. 3. Its S.J. unit is newton (N).

(b)

The force excerted by the earth on the moon is 2.01 x 10²⁰ N.

(c) (i) Object A is moving with a constant speed because it is covering equal distances in each second throughout.
(ii) Object C is moving with a constant acceleration because its speed is increasing at a constant rate each second. The value of this acceleration is 40 cm s^-2.
(iii) Object B is moving with a variable acceleration because its speed changes are seen to be irregular.
(iv) Total distance covered by A in 5 seconds = (5 x 20) cm = 100 cm
Total distance covered by B in 5 seconds = (20 + 36 + 24 + 30 + 48) cm
= 158 cm Total distance covered by C in 5 seconds
= (20 + 60 + 100 + 140 + 180) cm
= 500 cm.

Question 7.
(a) A glass jar is kept at a place where the acceleration due to gravity has a value ‘g’ It is filled up to a height ‘h’ with a liquid of density ‘d’. The atmosphere pressure at the place has a value PA.
(i) How much is the pressure at the free surface of the liquid ?
(ii) What would be the total pressure at a point on the base of a jar ?
(iii) Give an expression for the lateral pressure at this depth on the inner side of the jar.

(b) (i) It is said that even a beginner is not likely to sink in the waters of the ‘dead sea’. Why is it so ?
(ii) Define the term ‘relative density of a substance’.

(c) For a given body, it is observed that it weighs 20 gf in air, 18.2 gf in a liquid and 18.0 gf in water. Find :
(i) the relative density of the body, and
(ii) the relative density of the liquid.
Answer:
(i) Pressure at free surface of the liquid = Atmosphere pressure = P_A.
(ii) The total pressure, at the base of the jar equals the sum of atmospheric pressure and the pressure due to liquid column of height 7z’.
∴ Total pressure at the base of the jar = P_A + hdg.
(iii) The lateral pressure at this depth on the inner scde of the jar will also be equal to the total pressure, e., lateral pressure = P_A + hdg.

(b)(i) The water of the dead sea is extremely salty. Its density is, therefore, much higher than that of fresh water and also more than the average density of the human body. It is because of this large value of density we can say that even a beginner is not likely to sink in the waters of this sea as the sea exerts upthrust more than the body weight.

(ii) The relative density of a substance is the ratio of its density to the density of pure water at 4°C, i.e.\(\text { R.D. }=\frac{\text { Density of given substance }}{\text { Density of pure water at } 4^{\circ} \mathrm{C}}\)

(c) Loss of weight of the body in water = (20 – 18) gf = 2 gf
Loss of weight of the body in liquid = (20 – 18.2) gf = 1.8 gf

Question 8.
(a) An object is placed at a distance of 2 cm from a plane mirror. If the object is moved by 1 cm towards the mirrors, what will be the new distance between the object and its image ?

(b) Fill in the blanks :
(i) When the rays do not actually meet, we get a …………… image.
(ii) Two parallel plane mirrors can be used to get …………. images of an object.
(iii) The image formed by a plane mirror is …………..with respect to the object.

(c) Redraw the following diagram. Complete it by drawing two rays to show the formation of the image of on object AB. What is the size, position and nature of the image formed ?

Answer:
(a) Initial distance between the object and its image = (2 + 2) cm = 4 cm.
Final distance between the object and its image = (1 + 1) cm = 2 cm.

(b) (i) Virtual (ii) Infinite (iii) Laterally inverted.

(c) The required rays are as shown. The image formed is :
(1) Smaller in size than the object,
(2) Formed between P and F, i.e., the pole and the focus of the mirror.
(3) Virtual in nature.

Question 9.
(i) Give three points of distinction between the propagation of sound and that of light.
(ii) A longitudinal wave of wavelength 1 cm travels in air with a speed of 330 ms^-1. Calcu­late the frequency of the wave. Can this wave be heard by a normal human being ?
(iii) Establish a relation between velocity, frequency and wavelength of a wave.
Answer:
(a) (1) The speed of light in air is 3 x 10⁸ ms^-1 whereas the speed of sound in air is 330 ms^-1 at 0°C.
(2) The speed of light decreases in an optically denser medium (speed of light in water is 2.25 x 10⁸ ms^-1, in glass is 2.0 x 10⁸ ms^-1), while the speed of sound is more in solids, less in liquids and least in gases.
(3) Light can travel in vacuum, but sound cannot travel in vacuum.

(b) Given : λ = 1 cm = 0.01 m,υ = 330 ms
We know,  υ =fλ
∴ \(f=\frac{\lambda}{v}=\frac{330}{0.01}=33000 \mathrm{~Hz}\)
No, this cannot be heard by a normal human being.

(c) Let the velocity of a wave be ‘υ’, time period ‘T’, frequency ‘f’ and wavelength ‘λ’. By the definition of wavelength.
Wavelength λ = Distance travelled by the wave in one time period, i.e., T second
= Wavelength × Time Period
or λ = υ × T
But \(\mathrm{T}=\frac{1}{f}\)
υ = f × λ

Question 10.
(a) Name the following :
(i) Instrument used to control current in an electric circuit
(ii) Instrument used to detect current
(iii) Instrument used to measure current.
(b) State three evidences to show the existence of earth’s magnetic field.
(c) A conductor carries a current of 0.4 A.
(d) Find the amount of charge that will pass through the cross-section of conductor in 16 s.
(e) How many electrons will flow in this time interval if charge on one electron is 1.6 x 10^-19 C ?
Answer:
(a) (i) Rheostat
(ii) Galvanometer
(iii) Ammeter.

(b) The existance of the earth’s magnetic field is based on the following facts :
(1) An iron piece buried inside the earth becomes a magnet.
(2) Neutral points are obtained when the lines of force of a bar magnet are drawn.
(3) A freely suspended needle always points in one direction (north-south direction).

(c) Given : I = 0.4 A, t = 16 s
(i) Charge = Current x Time
or Q = I x t = 0.4 x 16 = 6.4 C
(ii) If V electrons flow and ‘e is the charge on one electron, then total charge passed
Q = ne
\(n=\frac{\mathrm{Q}}{e}=\frac{6.4}{1.6 \times 10^{-19}}=4 \times 10^{19}\)

ICSE Class 9 Physics Question Papers with Answers

ICSE Class 9 Physics Sample Question Paper 1 with Answers

[Max Marks : 80
[2 Hours]

General Instructions

• Answers to this Paper must be written on the paper provided separately.
• You will not be allowed to write during the first 15 minutes.
• This time is to be spent in reading the question paper.
• The time given at the head of this Paper is the time allowed for writing the answers.
• Section I is compulsory. Attempt any four questions from Section II.
• The intended marks for questions or parts of questions are given in brackets [ ].

Section – I
(Attempt all questions from this section) [40 Marks]

Question 1.
(a) (i) Define the least count of an instrument. [2]
(ii) What is the Least count of a standard laboratory micrometer screw gauge?
(b) A spring balance is used to find the weight of a body X on the surface of the moon. The mass of the body X is 2 kg and its weight is recorded as 3.4 N. The weight of another
body Y recorded by the same balance is found to be 7.65 N. Calculate the mass of the body Y. [2]
(c) State two differences between mass and weight. [2]
(d) Two pendulums P and Q have equal lengths but their bobs weigh 10 gf and 20 gf respectively. [2]
(i) Compare their time periods.
(ii) Give a reason for your answer.
(e) Why do we need to run a certain distance before getting into a moving bus? [2]
Answer:
(a) (i) The least count of an instrument is the smallest measurement that can be taken accurately with it.
(ii) The least count of a standard laboratory micrometer screw gauge is 0.0001 cm.

(b)

(c)

	Mass	Weight
	Mass is a scalar quantity.	Weight is a vector quantity.
	Its S.I. unit is kilogram (kg)	Its S.I. unit is newton (N).

(d) (i) 1:1.
(ii) Time period does not depend upon the weight of the bob.

(e) The reason is that by running, we bring our body in the state of motion. When the body is in motion, it is easier to get into a moving bus.

Question 2.
(a) Copy the diagram below and clearly mark the directions of the forces that act on it and name the forces. [2]

(b) If I travel from Mumbai to Pune (150 km) in 2 1/2 hrs via the Express Highway and return to Mumbai via the old Highway (180 km) in 3 1/2 hrs, calculate the average velocity during the entire journey. [2]
(c) Define retardation and give an example of a body having this motion. [2]
(d) Copy the diagram and complete the path of the rays A and B. [2]

(e) State the purpose of using the following in an electric circuit.  [2]
(i) Ammeter
(ii) Rheostat
Answer:
(a) The completed diagram is shown alongside. The weight acts downwards and the tension acts upwards.

(b) The average velocity is zero because the displacement is zero.

(c) Retardation is defined as the decrease in velocity per second.
For example, a train approaching a station must have retardation in order to stop.

(d)

Question 3.
(a) A sound wave of frequency 500 Hz and wavelength 0.66 m is travelling in a medium. Calculate the velocity of the wave in the medium.   [2]
(b) Sound waves A and B are travelling in two different media.
Find which wave will be travelling faster, when [2]
(i) A is travelling in water and B is travelling in CO₂.
(ii) A is travelling in CO₂ and B is travelling in hydrogen. Also support your answers with reasons.
(c) A body is completely immersed in a fluid. State two factors on which the upthrust acting on the body depends. [2]
(d) A and B are two metal spheres which are connected with the help of a metal wire. State the direction of flow of electrons in each case. [2]

(e) Why do we use a convex mirror as a rear view mirror ? [2]
Answer:
(a) Given : f = 500 Hz, λ = 0.66 m
We know that, υ = fλ
= 500 x 0.66 330 ms^-1

(b) (i) Speed of sound wave in a liquid is greater than the speed in a gas. Hence, wave A travelling in water will travel faster than wave B travelling in carbon dioxide.
(ii) Speed of sound is inversely proportional to density of medium. Hence, wave B travelling in hydrogen will have more speed than wave A travelling in carbon dioxide.

(c) Upthrust on a body due to a fluid depends on the following two factors :
(1) Volume of the body submerged in liquid (or fluid), and
(2) Density of the liquid (or fluid) in which the body is submerged.

(d) (i) A to B
(ii) B to A.

(e) A convex mirror diverges the incident light beam and always forms a virtual, small and erect image between its pole and focus. This fact enables the driver to use it as a rear view mirror in vehicles to see all the traffic approaching from behind.

Questions 4.
(a) State two differences between an electromagnet and a permanent magnet. [2]
(b) Why does a magnet suspended freely from its C.G., always come to rest along the north south direction of the earth ?  [2]
(c) State the second law of thermodynamics in energy flow. (Law of conservation of energy) [2]
(d) Name and state the principle on which the hydraulic brakes of a car work. [2]
(e) State two main human activities which are responsible for the increase of carbon dioxide gas in the atmosphere.  [2]
Answer:

	Electromagnet	Permanent Magnet
	An electromagnet is made of soft iron.	A permanent magnet is made of steel.
	The polarity of an electromagnet can be reversed.	The polarity of a permanent magnet can not be reversed.

(b) A magnet suspended freely from its C.G. always comes to rest along the north-south direction of the earth because the north pole of the magnet points towards the geographic north where there is a magnetic south pole attracting it. Similarly, the south pole of the magnet points towards the geographic south where there is a magnetic north pole attracting it.

(c) According to the second law of thermodynamics, when energy is put to work, a part of it is always converted in unuseful form as heat, mainly due to friction and radiation.

(d) The hydraulic brakes of a car work on the principle of hydraulic machine. The principle of each hydraulic machine is that a small force applied on a smaller piston is transmitted to produce a large force on the bigger piston.

(e) Two human activities responsible for the increase of carbon dioxide gas are as follows :
(1) The burning of fuels, and
(2) Increase in population.

Section – II          
(Attempt any four questions from this section) [40 Marks]

Question 5.
(a) A train is moving at a velocity of 25 ms^-1. It is brought to rest by applying the brakes which produces a uniform retardation of 0.5 ms^-2. Calculate : [3]
(i) The velocity of the train after 10s.
(ii) If the mass of the train is 20000 kg then calculate the force required to stop the train.

(b) (i) State the universal law of gravitaiton. [4]
(ii) Express it in a mathematical form. (Explain the symbols used.)
(iii) State the value of universal gravitational constant in S.I. unit.

(c) Using the following velocity time graph of a body answer the following questions.

(i) During which time intervals is the body moving with variable velocity ?
(ii) What is the acceleration of the body during the interval 3s to 5s ?
(iii) What is the displacement of the body in the last four seconds of its motion ?
Answer:
(a) (i) Given : u = 25 ms^-1, cv= -5 ms^-2, t = 10 s
v = u + at
= 25 + (- 0.5) x 10 = 25 – 5 = 20 ms^-1

(ii)   m = 20000 kg
F = ma = 20000 x 0.5 = 10000 N.

(b) (i) According to Newton’s universal law of gravitation, the force of attraction acting between the two particles is (1) directly proportional to the product of their masses and (2) inversely proportional to the square of the distance between them.

(ii) Let there be two particles of masses m₁ and m₂ at a separation of r. The magnitude of force of attraction F acting between them is :
\(\mathrm{F}=\mathrm{G} \frac{m_{1} m_{2}}{r^{2}}\)

(iii) The value of gravitational constant G is 6.67 x 10^-11 Nm² kg^-2.

(c) (i) From O to 3 s, and 5s to 7 s
(ii) Zero
(iii) Displacement in the last 4 seconds
= Area of trapezium BCDE

Question 6.
(a) (i) Differentiate between the terms supersonic and ultrasonic. [3]
(ii) State two uses of ultrasound.
(b) State three factors on which the speed of sound depends. [3]
(c) The speed of sound in air is 320 ms^-1 and in water it is 1600 ms^-1. It takes 2.5 s for sound to reach a certain distance from the source placed in air.  [4]
(i) Find the distance.
(ii) How much time will it take for sound to travel the same distance when the source is in water ?
Answer:
(a) (i) Sound of frequency above 20 kHz is called ultrasound or ultrasonic sound whereas supersonic refers to an object which travels with a speed greater than the speed of sound in air.
(ii) Ultrasound is used for making cuts of desired shape in materials like glass. It is also used in surgery to remove cataract.

(b) The speed of sound in a gas is affected by the change in :
(1) Density : Speed of sound is inversely proportional to the square root of density of the gas.
(2) Temperature: The speed of sound in a gas increases with the increase in temperature of the gas.
(3) Humidity : The speed of sound in air increases with the increase in humidity in air.

(c) (i) In air : Speed (v) = 320 ms^-1
Time (t) =  2.5s
∴ Distance (d) = v x t
= 320 x 2.5 = 800 m

(ii)  In Water : Speed (v) = 1600 ms^-1
Distance (d) = 800 m
\(\text { Time }(t)=\frac{d}{v}=\frac{800}{1600}=0.5 \mathrm{s}\)

Question 7.
(a) The diagrams below show pins suspended from the same magnet to their maximum limit in two different cases. State, with a reason, whether the set of pins A or the set of pins B are made out of soft iron. Also define the magnetic process which enables us to suspend the pins one below the other. [3]

(b) (i) Define a secondary cell. [3]
(ii) Give one example of a secondary cell.
(iii) State one advantage of a secondary cell over a primary cell.

(c) (i) Define a neutral point. [4]
(ii) In the diagram below AB is a magnet and CD is an iron bar.
Study the diagram and determine the polarities at the ends A, B and D.

Answer:
(a) Set of pins A are made out of soft iron because the set of pins A have acquired a stronger magnetic field strength as compared to the set of pins B. The process which enables us to suspend the pins is called induced magnetism. The temporary magnetism acquired by a magnetic material when it is kept near (or in contact with) a magnet is called induced magnetism.

(b) (i) A secondary cell is a cell which provides current as a result of chemical reaction which is reversible and so they can be recharged.
(ii) Lead accumulator is an example of a secondary cell.
(iii) A secondary cell can be recharged whereas a primary cell cannot be recharged.

(c) (i) Neutral point is a point where the magnetic field of magnet is equal in magnitude to the earth’s horizontal magnetic field, but it is in opposite direction. Thus, the resultant (or net) magnetic field at the neutral points is zero.
(ii) A is north pole, B is south pole and D is north pole.

Question 8.
(a) The area of pistons in hydraulic machine are 6 cm² and 576 cm². What force on the smaller piston will support a load of 1152 N on the larger piston ?  [3]
State assumption made in the above calculation.

(b) (i) Define global warming. [3]
(ii) State two ways by which global warming impacts on life on earth.

(c) Complete the path of the ray AB over plane mirrors M₁ and M₂ and label all the angles of incidences. [4]

Answer:
(a)

Hence, force on smaller piston is 12 N. The assumption is that there is no friction or leakage of liquid

(b) (i) Global warming is the increase in average effective temperature near the earth’s surface due to an increase in the amount of green house gases in its atmosphere
(ii) Due to global warming, there is a change in blooming season of different plants. There is also an increase in heat stroke deaths.

(c) The complete ray diagram is as follow :

Question 9.
(a) (i) Why does a piece of steel sink in water but float on mercury ? [3]
(ii) If a bowl is formed from the same steel piece then it can float in water. Why ?

(b) The diagram below shows a frozen pond in a cold region. [3]
(i) State the expected temperatures at A and B.
(ii) Name the phenomenon responsible for these temperature mentioned in part (i).

(c) A metal piece weighs 200 gf in air and 150 gf when completely immersed in water. [4]
(i) Calculate the relative density of the metal piece.
(ii) How much will it weigh in a liquid of density 0.8 g cm^-3?
Answer:
(a) (i) Mercury has a higher density than steel so it produces a greater upthrust which enables the piece of steel to float on it, but in case of water, the upthrust produced is less than the weight of the steel piece as the density of water is less than that of steel. Hence, it sinks in water.
(ii) When the bowl is formed from the same piece of steel, it can float on water because its volume increases and it will displace a greater volume of water thereby increasing the upthrust.

(b) (i) Temperature at A is 0°C and temperature at B is 4°C.
(ii) The phenomenon responsible for the mentioned temperatures is the anomalous expansion of water.

(c) Given : Weight of metal in air (w₁)= 200 gf
Weight of metal in water (w₂) = 150 gf
(i) Relative density of metal piece =\(=\frac{w_{1}}{w_{1}-w_{2}}=\frac{200}{200-150}=4\)

(ii) Density of liquid = 0.8 g cm^-3
Relative density of liquid = 0.8
Let , Weight of metal in liquid = w₃

Question 10.
(a) Copy and complete the following ray diagram to obtain the image of the object AB kept in front of the concave mirror. [3]

(b) An object of height 20 cm is kept at a distance of 48 cm in front of a mirror of focal length 12 cm. If the mirror forms a virtual, diminished image of the object then calculate : [3]
(i) the distance of the image from the mirror.
(ii) its magnification.

(c) Study the diagram below and [4]
(i) Identify the electrical components labelled A, B and C.
(ii) State whether the circuit given below is open or closed.

Answer:
(a) The complete diagram is as drawn below.

(b) Since the image formed is virtual and diminished, the mirror used is convex.
Given : f = 12 cm (positive)
u = 48 cm (negative)
Using the relation,


Thus, the image is formed at a distance of 9.6 cm behind the mirror.
(ii) Magnification (m) \(=\frac{-v}{u}=\frac{-9.6}{(-48)}=\frac{1}{5}\)
Thus, the size of the image is one-fifth the size of the object.

(c) (i) A is the switch, B is the fixed resistance, and C is the cell,
(ii) The given circuit is open.

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