XI B 1 of 3

ITL Public School Annual examination (2014-15)

Date: 11.02.2015 Class: XI Physics (042) (Set -B)

Time:3 hrs M. M: 70 General Instructions:

1. All questions are compulsory. There are 26 questions in all. 2. This question paper has five sections. 3. Section A contains five questions of one mark each, Section B contains five questions of two

marks each, Section C contains twelve questions of three marks each, Section D contains one value based question of four marks and Section E contains three questions of five marks each.

4. There is no overall choice. However, an internal choice has been provided in one question of two marks, one question of three marks and all three questions of five marks each. You have to attempt only one of the given choices in such questions.

Section - A

1 A ball of mass 5 kg strikes against a wall at an angle of 450 and is reflected at the same angle. Find

the change in momentum.

1

2 What is the condition to be satisfied for a mass tied to a string to perform a vertical circle?

1

3 Write equation of S.H.M. having following characteristics:

Amplitude = 0.01 m, frequency = 60 Hz, initial phase =

1

4 What is analogous to mass in rotational motion?

1

5 Two sound sources produce 12 beats in 4 seconds. By how much do their frequencies differ? 1

Section - B

6 A stone is thrown horizontally with a speed √ from the top of a wall of height h. It strikes the

level ground through the foot of the wall at a distance x from the wall. What is the value of x?

2

7 The moment of inertia of two rolling bodies A and B are IA and IB (IA > IB) and their angular

momenta are equal. Which one has greater kinetic energy? Explain.

2

8 If P, V and T are pressure, volume and temperature respectively of gas, then from the relation

) ) , find the dimensions of a and b.

2

9 State and prove work energy theorem for a variable force.

OR

Distinguish between conservative and non-conservative forces with one example each.

2

10 A liquid drop of diameter of 4 mm breaks into 1000 droplets of equal size. Calculate the resultant

change in energy (the surface tension of liquid is 0.07 N/m).

2

Section -C

11 The string of a pendulum is 2.0 m long. The body is pulled sideways so that the string becomes

horizontal and bob is released. What is the speed with which the bob is released? What is the speed

which the bob arrives at the lowest point? Assume that 10% of the initial energy is used against air

resistance.

3

12 (i) State parallel-axes and perpendicular axes theorem.

(ii) What is the moment of inertia about an axis passing through the edge as a tangent in the plane

of a disc of mass M and radius ‘r’?

3

13 Derive an expression for variation of acceleration due to gravity with altitude.

The acceleration due to gravity on the surface of moon is 1.7 m/s2. What is the time period of a

simple pendulum on the moon if its time period is 3.5 s on earth?

3

XI B 2 of 3

14 A liquid is in a streamline flow through a pipe of non-uniform cross-section. Prove that the sum of

its kinetic energy, pressure energy and potential energy per unit volume remains constant.

3

15

Three bodies A, B and C each of mass m are hanging on a string over a fixed pulley, as shown in

fig. What are the tensions in the strings connecting bodies A to B and B to C?

3

16 On the basis of kinetic theory, derive an expression for pressure exerted by an ideal gas.

3

17

Write Newton’s formula for the speed of sound in air. What was wrong with this formula? What

correction was made by Laplace in this formula?

OR

i. What is geometrical meaning of S.H.M.?

ii. If y1= 5cos ωt and y2= 5 [ √ cos ωt + sin ωt], find the ratio of the amplitudes of two waves.

3

18 What is capillarity? Derive an expression for the height to which the liquid rise in the capillary tube

of radius r. Explain What happens when the length of a capillary tube is less than the height upto

which the liquid may rise in it.

3

19 A wooden ball of density ρ is immersed in water of density σ to depth h and then released. Find the

height H above the surface of water upto which the ball jumps out of water.

3

20 What is a progressive wave? Derive an equation for a plane progressive harmonic wave.

3

21 State the law of equipartition of energy of a dynamic system and use it to find the values of internal

energy and the ratio of the specific heats of a (i) monatomic (ii) diatomic and (iii) triatomic gas

molecules.

3

22 What is escape velocity? Obtain the expression for the escape velocity on earth. Why is it that there

is no atmosphere on the moon? Explain.

3

Section D

23 Meenu was afraid of going anywhere by air. Once, she couldn’t avoid going by an aeroplane. Her

friend Kavita, who knew her problem, was with her. Inside the plane, Kavita saw that Meenu was

very quiet and feeling uncomfortable. She tried to talk to Meenu but she didn’t answer. As the

plane was about to take off, Kavita started fighting with Meenu without any cause for diverting her

mind. While flighting, Meenu didn’t realize that plane had taken off and now she was in air. She

felt very happy to overcome her fear.

i. What values do you associate with Kavita?

ii. An aeroplane takes off at an angle of 300 to the horizontal. If the component of its velocity

along the horizontal is 250 km/h. What is its actual velocity? Find also the vertical

component of velocity.

iii. The blades of an aeroplane propeller are rotating at the rate of 600 revolutions per minute.

Calculate its angular velocity.

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XI B 3 of 3

Section E

24 (I) What is Doppler’s effect of sound? Obtain an expression for apparent frequency of sound when

source and listener are approaching each other in a moving medium.

(II) A train, standing at the outer signal of a railway station blows a whistle of frequency 400 Hz in

still air. (i) What is the frequency of the whistle for a platform observer when the train

(a) approaches the platform with a speed of 10 m s–1

, (b) recedes from the platform with a speed of

10 m s–1? (ii) What is the speed of sound in each case? The speed of sound in still air can be taken

as 340 m s–1

OR

(I) Prove analytically that in the case of a closed organ pipe of length L, the frequencies of the

vibrating air column are given by )

(II) The transverse displacement of a string (clamped at its both ends) is given by

)

) )

Where x and y are in m and t in s. The length of the string is 1.5 m and its mass is 3× 10–2

kg.

Answer the following :

(a) Does the function represent a travelling wave or a stationary wave?

(b) Interpret the wave as a superposition of two waves travelling in opposite directions. What is

the wavelength, frequency, and speed of each wave?

(c) Determine the tension in the string.

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25

(a)What is the principle of a heat pump? Explain the working of a heat pump with a block diagram

and obtain an expression for its coefficient of performance.

(b) Assuming that a domestic refrigerator can be regarded as a reversible engine working between

the temperature of melting ice and that of atmosphere (17oC), calculate the energy which must be

supplied to freeze one kilogram of water already at 0o C.( latent heat of fusion of ice = 3.3 × 10

5

Jkg-1

)

OR

A monoatomic ideal gas of two moles is taken through a

cyclic process starting from A as shown in fig. The volume

ratios are

and

. If the temperature TA at A is 27

0C , calculate,

(a) the temperature of the gas at a points B,

(b) heat absorbed or released by the gas in each process

(c) the total work done by the gas during the complete cycle.

mention your answer in terms of the gas constant R.

5

26 a) What is projectile? Derive the expression for the trajectory, maximum height, time of flight,

and horizontal range for a projectile thrown upward, making an angle θ with the horizontal

direction.

b) What will be the effect on maximum height of a projectile when its angle of projection is

changed from 300 to 60

0, keeping the same initial velocity of projection?

OR

(a) What is centripetal acceleration? Find its magnitude and direction in case of uniform

circular motion.

(b) Derive a relation for the optimum velocity of negotiating a curve by a body in a banked

curve.

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