**SESSION ENDING EXAMINATION**

**CLASS XI**

**PHYSICS**

**M.MARKS:70**

** TIME 3 HRS**

*General Instructions:*

*All questions are compulsary**There are 30 questions in total. Questions 1 to 8 carry 1 mark each. Questions 9 to 18 carry 2 marks each. Questions 19 to 27 carry 3 marks each and questions 28 to 30 carry 5 marks each.**Use of calculators is not permitted.*

********Choices are avoided as this is a question paper meant for practice ***********
**

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- Write the ratio of AU and A
^{o.} - A truck and a car moving with the same kinetic energy are stopped by applying the same retarding force. Which will stop at a smaller distance?
- In which motion linear momentum changes but kinetic energy does not?
- What is the time period of simple pendulum at the centre of earth?
- Write the SI unit and dimensional formula for Gravitational constant.
- Why is it difficult to stop bleeding from cut in human body at high altitudes?
- When air is blown between two balls suspended close to each other, they are attracted towards each other. Why?
- If pressure of a gas at constant temperature is increased four times, how the velocity of sound in the gas will be affected?
- A train moves away from a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by observer is f1. If the train speed is reduced to 17 m/s, the frequency registered is f2. If the speed of sound is 340 m/s, then find f1/f2.
- Show that impulse of a force is equal to the change in momentum produced by the force.
- Derive expression for particle velocity during simple harmonic motion.
- Write the dimension of a and b in the relation F = ax + bt
^{2} - A particle is projected with velocity u making an angle with the vertical. Write the formula for (a) time of flight (b) horizontal range.
- Two bodies A and B having masses 5 kg and 6 kg respectively have equal momenta. Find their kinetic energies.
- Find the moment of inertia of a sphere about a tangent to the sphere, given moment of inertia of the sphere about any of its diameter is 2/5 MR
^{2}, where M is the mass of the sphere and R its radius. - Define Cp and Cv. Write the relation between them.
- Find the degrees of freedom for (a) diatomic gas (b) linear triatomic molecule
- An incident wave is represented by y = 20 sin (2x – 4t). Write the expression for the reflected wave (i) from rigid boundary (ii) from an open boundary.
- Derive the eqution s = ut + 1/2 at
^{2} - Three identical blocks of masses m =2kg connected by strings are drawn by a force 10.2 N on a frictionless surface. Find the tension in the string between the second and the third blocks.
- Define elastic collission. Prove that bodies of identical masses exchange their velocities after head on collision.
- Define centre of mass. The distance between the centres of carbon and oxygen atoms in the carbon monoxide gas molecule is 1.13 Ao. Locate the centre of mass of the gas molecule relative to the carbon atom.
- Define escape velocity. Obtain an expression for escape velocity of the body from the surface of earth
- Eight rain drops of radius 1 mm each falling down with terminal velocity of 5 cm /s combine to form a bigger drop. Find the terminal velocity of the bigger drop.
- Define isothermal process. Derive an expression for the work done in an isothermal process.
- Derive an expression for the pressure exerted by an ideal gas using the assumptions of kinetic theory of gases.
- Write the formula for kinetic energy, potential energy and total energy of a body executing SHM. Prove that the total energy is directly proportional to square of amplitude and frequency.
- (i)Define centripetal acceleration. Derive an expression for the centripetal acceleration of a body moving with uniform speed v along a circular path of radius r

(ii) In projectile, a particle is projected such that magnitude of velocity at the topmost point is half of the magnitude of initial velocity. Find the angle of projection - (i)State and prove law of conservation of linear momentum (ii) A machine gun has a mass 20 kg. It fires 35 g bullets at the rate of 4 bullets per second with the speed of 400 m/s. What force must be applied to the gun to keep it in position?
- (i) Derive capillary ascent formula. (ii) Draw stress strain curve for a metallic wire, when stretched up to the breaking point. Also label each point in the graph.

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