Central Board of Secondary Education (CBSE)

**Sample Paper – 2012**

**Class – XI**

Subject –** Physics**

1. Define absolute zero according to kinetic interpretation of temperature.

2. What happens when a capillary tube of insufficient length is dipped in a liquid?

3. Write the full name of technique used in locating

(a) An under water obstacle

(b) Position of an aero plane in space.

4. How is its orbital velocity related with velocity of escape from that planet? A satellite revolves close to the surface of a planet.

5. If the change in the value of g at a height h above the surface of earth is same as that at a depth x below it (both x and h being much smaller than radius of earth), then how are x and h related to each other?

6. How can we differentiated btween velocity of wave and velocity of particle? Obtain the relation for the velocity of wave in wave motion.

7. Draw the graphical representation of simple harmonic motion, showing the

(a) Velocity-time curve

(b) Acceleration-time curve

(c) Displacement-time curve

8. Calculate the number of molecules in 2×10^{-6} m^{3 }of a perfect gas at 27^{0} C and at a pressure of 0.01 m of mercury. Mean kinetic-energy of a molecule at 27^{0}C=4×10^{-11}J and g =9.8 ms^{-2}

^{ }9. What is the relation between specific heat of gas at constant pressure and at constant volume, when the amount of gas is one gram molecule.

10. Define an expression for energy stored in a wire due to extension.

11. Two syringes of different cross section, filled with water are connected with a tightly fitted rubber tube with water. Diameters of the smaller and larger piston are 1.0 cm and 3.0 cm respectively.

(a) Explain about force exerted on the larger piston when a force of 10 N is applied to the smaller piston.

(b) How does the larger piston move out If the smaller piston is pushed in through 6.0 cm ?

12. Newton’s third law of motion follows from theNewton’s second law of motion. Prove it.

OR

Obtain an expression for the angle which a cyclist will have to make with the vertical, while taking a circular turn. [For successful negotiation]

13. A steel ball of radius r allowed to fall under gravity through a viscous liquid of coefficient of viscosity η. After some time, the velocity of the ball attains a constant value v_{t}. The terminal velocity depends upon

(a) Weight of the ball mg

(b) The coefficient of viscosity η

(c) The radius of the ball r

By method of dimensions determine the relation expressing terminal velocity.

14. The diagonals of a parallelogram are represented by R_{1}=3i +2j -7k and R_{2}= 5i+ 6j-3k. Find the area of parallelogram.

OR

Find the angular velocity of (a) hour hand of clock (b) second hand of clock and (c) of earth about its own axis.

15-A projectile is fired with velocity u making an angle θ with the horizontal form the surface of earth. Prove that the projectile will hit the surface of earth with same velocity and same angle.

16. Drive position time relation of a body moving with a constant acceleration and discuss it graphically.

17. A bullet of mass 0.012 kg and horizontal speed 70ms^{-1}strikes the block of wood of mass 0.4 kg and instantly comes to rest with respect to the block. The block is suspended from the ceiling by means of thin wires. Calculate the height to which the block rises and the amount of heat produced in the block.

18. What do you mean by torque? Give its unit. Show that it is equal to the product of force and the perpendicular distance of its line of action from its axis of rotation.

19. Drive an expression for the kinetic energy of a body rotating about a given axis and find a definition for moment of inertia of the body in terms of kinetic energy of rotation.

20. law of conservation of mechanical energy for a body falling freely and discuss it graphically also. Prove that

21. What is limiting friction? it is always convenient to pull a heavier body than to push it on the surface. Prove

22. Find the expression of total energy of a satellite revolving around the surface of earth. What is the significance of negative sign in the expression?

23. What do you by an ideal simple pendulum? Define an expression for its time period.

24. A rocket is moving at a speed of 200 ms^{-1} towards a stationary target. While moving, it emits a wave of frequency 1000 Hz. On reaching the target, sound gets reflected back to the rocket as an echo. Calculate,

(a) The frequency of sound as detected by target and

(b) The frequency of echo as detected by rocket (taking speed of sound 330ms^{-1})

25. (a) Obtain an expression for the centripetal force required to make a body of mass m moving with a velocity v around a circular path of radius r.

(b) Find an expression for the velocity of recoil gun.

OR

What is the acceleration of the block and trolley system shown, if the coefficient of kinetic friction between the trolley and surface is 0.04? What is the tension in the string? (g =10 ms^{-2}). Neglect the mass of the string.

26. What is Carnot’s engine? Drive an expression for its efficiency.

OR

State mathematically, first law of thermodynamics and use it to find the expression for work done during adiabatic expansion. Write two limitations of first law of thermodynamics.

27. State and prove Bernoulli’s theorem. Name any two application of Bernoulli’s principle.

OR

What is capillarity? Drive an expression for the capillary rise of a liquid in a tube.

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