## 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 ?
(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. (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. (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 ?
(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.

 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.
(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.
(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.
(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.
(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.
(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.