**Sample Paper – 2009**

**Class – XI**

**Subject - ****Physics**

TIME: 3hr. MM: 70

General Instructions.

1. Questions from question no. 1-8 carry 1marks each, 9-18 carry 2 marks each, 19-27 carry 3 marks each and 28-30 carry 5 marks each.

2. There is no overall choice but one choice is given in 2 marks question, two choice in 3 marks question and all three choices in five marks question

3. You may use the following physical constant where ever necessary:

Speed of light C = 3 x 10^{8} ms^{-1}^{}

Gravitational constant G= 6.6 x 10^{-11} NM^{2} Kg^{-2 }

Gas constant R= 8.314 J Mol^{-1} k^{-1}

Mass of electron = 9.110 x 10^{-31} Kg

Mechanical equivalent of heat = 4.185 J Cal^{-1 }

Standard atmospheric pressure = 1.013 x 10^{5} Pa

Absolute zero 0k = - 273.15^{0}c

Acceleration due to gravity = 9.8 Ms^{-2}

^{ }

1. If a composite physical quantity in terms of moment of inertia I, force F, velocity V,

work W and length L is defined as,

Q = (I F V^{2} /WL^{3})

Find the dimension of Q and identify it.

2. Explain why a man who fall from a height on a cemented floor receive more injury

then when he fall from the same height on the heap of sand.

3. Is it possible to have a collision in which all the kinetic energy is lost? If so cite an example.

4. You are given two spheres of the same mass, size and appearance, but one of them is solid while the other hollow. If they are allowed to roll down an incline which

One will reach the bottom first?

5. Can every oscillatory motion be treated as simple harmonic motion in the limit of small amplitude?

6. If the earth be at one half its present distance from the sun how many days will their be in a year?

7. A 25 cm long tube closed at one end is lowered with his open end down into a fresh water lake. If one- third of the tube is filled with water then what is the distance between the surface of lake and level of water in the tube.

8. Why zeroth law of thermodyamics is not called as IIIrd law though it was discovered after I and II law?

9. Define uniform velocity of an object moving along a straight line. What will be shape of velocity time and position time graphs of such a motion?

10. What do you mean by a projectile? A projectile is fired with velocity v making an angle Ө with the horizontal. Show that its path is parabolic.

11. Define the term momentum and impulse also derives the relation between them.

12. Define and explain moment of inertia of a rigid body about an axis of rotation. Hence define radius of gyration.

13. What do understand by gravitational field and gravitational field intensity? Show that acceleration due to gravity is a measure of the gravitational field of earth at a point.

OR

Define escape velocity. Derive an expression for escape velocity of an object from

the surface of a planet.

14. Explain terminal velocity and mention its importance. Derive stokes law

dimensionally.

14. State newton’s law of cooling. Deduce the relation

log (Ө- Ө_{0}) = - k t + c

15. In a refrigerator, heat from inside at 277K is transferred to a room at 300K. How many joule of heat will be delivered to the room for each joule of electrical energy consumed ideally?

16. Give the essential features of the kinetic theory of gases. Show that the pressure exerted by a gas is equal to two-thirds the of the average kinetic energy per unit volume of the gas molecule.

17. State

18. What are centripetal acceleration and centripital force? Derive expression for them.

19. What is elastic collision? Calculate the velocities of the two bodies undergoing elastic collision in one dimension.

20. Show that the acceleration of free fall g at the surface of earth and the gravitational constant G are related by the expression

g = 4\3 Π p G R,

22. State the conditions, which are necessary for a satellite to appear stationary. Show

how an satellite orbiting round earth obey Kepler’s third law.

23. Find the maximum length of a steel wire that can hang without breaking.

Given that breaking stress for steel = 7.9 x 10^{11} N M^{-2} and density of steel =7.9 x

10^{3} Kg M^{-3}

OR

Define young’s modulus of elasticity, normal stress and longitudinal strain. Give

units of each of them. Derive elastic potential energy of a wire when stretched.

24. The weight of a body in water is one third of its weight in air. What is the density

Of the material of the body.

OR

What is stokes law? Explain terminal velocity and mention its importance

25. Show that for a carnot engine, efficiency of the engine is >_{}

η = 1- T_{2}/T_{1 }(T_{2 }>_{ }T_{1})

Where T_{1 } is the temperature of the source and T_{2} is the temperature of the sink.

26. If the orbital velocity of moon is increased by 42% than what will happen to its

position? Explain.

27. Define angular momentum for a system and show that

Angular momentum = Linear momentum x Perpendicular distance from axis of

rotation.

28. A body of mass 1 Kg initially at rest is moved by a horizontal force of 0.5 N on a

smooth friction less table. Calculate the work done by the force in 10 S and show

that it is equal to the change in kinetic energy of the body.

OR

Show that torque is the product of moment of inertia and angular acceleration. Also

prove that torque is the rate of change of angular momentum. Hence state the law of

conservation of angular momentum.

29. Establish Bernoulli’s equation for liquid flow, stating separately the assumption

made. What does the equation essentially represent?

OR

What should be the average velocity of water in a tube of diameter 0.4 Cm, so that

the flow is (a) laminar, (b) turbulent. The viscosity of water is 10^{-3} N M^{-2} S

30. What is Doppler effect. Derive an expression for the apparent frequency of sound

due to Doppler effect in the following case:

(a) When the listener moves towards the stationary source.

(b) When the source moves towards the stationary listener.

OR

Two notes of wavelength 2.04 metres and 2.08 metres produce 200 beats per minute in

a gas. Find the velocity of sound in the gas.