## Physics sample question paper according to the **New Pattern of CBSE 2020**.

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**MODEL PAPER**

**Grade: XI Subject: PHYSICS **

**Marks: 70 Time: 3hrs**

*General Instructions***:**

*a) All the questions are compulsory.*

*b) There are37 questions in total.*

*c) This question paper contains four sections: Section-A, Section-B, Section-C and Section-D*

*d) Section-A contains 20 questions of one mark each.*

*e) Section-B contains 7 questions of two marks each.*

*f) Section-C contains 7 questions of three marks each.*

*g) Section â€“D contains 3 questions of five marks each.*

__SECTION â€“ A__

1. The special theory of relativity explained by

a) Thomas Alva Edison b) Ampere

c) Albert Einstein d) C V Raman

2. Among the given following units which one is the longest unit of length?

a) Angstrom b) Fermi

c) Barn d) Parsec

3. Dimensional formula of universal gravitational constant______________

a) MLT-2 b) ML-1T-2

c) M-1LT-2 d) None of the above

4. What is the angle between i and j ____________

5. Which of the following statement is not true regarding Newtonâ€™s third law of motion?

a) To every action there is always an equal and opposite reaction

b) Action and reaction act on the same body

c) There is no cause-effect relationship between action and reaction

d) Action and reaction forces are simultaneous

6. For â€˜nâ€™ particles in space, the suitable, the suitable expression for the *x-*coordinate of the center of mass of the system is

7. What happens when the angular velocity of the Earth increases?

a) Acceleration due to gravity decreases at the equator

b) Acceleration due to gravity increases at the equator

c) moment of inertia of the earth increases

d) None of the above

8. The elasticity of a material can be altered by

a) annealing b) hammering

c) adding impurities d) all of the above

9. The amount of heat that a body can absorb by radiation___________

a) depends on the color of the body only

b) depends on the temperature of the body only

c) depends on color and temperature of the body only

d) depends on the density of the body

10. The average energy associated with three translational degrees of freedom is ________

11. Dimensional formula of viscosity is _______________

12. Two masses of 1g and 4g are moving with equal kinetic energy. The ratio of the magnitudes of

their velocity is _____________

13. Orbital velocity of satellite on the surface of earth is approximately _______________ km/s

*Or*

1 atmosphere = ________________________ N/m2

14. The efficiency of Carnot engine working between sink and source of temperatures 100k and 400k is ___________________

16. What is the relation between the initial velocity of the projectile and the time of flight?

17. Define Rigidityâ€™s modulus of elasticity.

18. What happens to the frequency of the pendulum when it took to the top of a mountain.

*Or*

A force of 5N acts on a body for 2 milli sec. If the mass of the body is 5g, calculate the change in

momentum.

19. Define the first law of thermodynamics.

20. Write the differences between longitudinal and transverse waves.

__SECTION - B__

21. What is the moment of inertia along a tangent of the sphere of mass m and radius R. Give the factors affecting the moment of inertia of the body?

22. Two stones are falling at a place from heights in the ratio 2.3 what is the ratio of their velocities

on reaching the ground.

23. The angular velocity of a wheel increases from 120 to 480 rpm in 10sec. The number of revolutions made during this time is?

*Or*

Derive the expression for Kinetic energy of a body vibrating in SHM.

24. The average depth of the Indian Ocean is about 3000 m. Calculate the fractional compression, of water at the bottom of the ocean. (given bulk modulus of water is 2.2 x 109 Nm-2 & g =10 ms-2)

*Or*

Derive an expression work done in an isothermal process. And Discuss the internal energy change in the isothermal process and adiabatic process.

25. State and explain Keplerâ€™s laws of planetary motion. And explain why hydrogen is in abundance around the sun but not around the earth?

26. What A liquid takes 3 minutes to cool from 800C to 600C. How much time will it take to cool from 600C to 400C? The temperature of the surroundings is 200C.

27. Define

a) Mean free path

b) Explain the effect of the pressure of the gas and diameter of the molecule on a mean free path.

__SECTION - C__

28. a) A lift is accelerated downward. Will the weight of the person inside the lift increase, decrease or remain the same?

b) If the lift is going up with uniform speed, then?

c) Explain the variation of g with height and depth..

29. Derive

30. State and prove perpendicular axis theorem. What is the moment of inertia for a circular disc of radius R and mass M along the tangent perpendicular to its diameter?

31. Describe the behavior of a wire under gradually increasing load.

*Or*

32. a) Define inertia and explain different types of inertia with examples.

b) If a table is to be taken from one corner of a room to another corner which is better pulling or pushing? Explain.

33. a) State and prove the work-Energy theorem. b) Give the units and dimensions for the co-efficient of restitution.

34. A spring-mass system is executing simple harmonic motion as shown below.

For this system

a. Write a general equation for the displacement, as a function of time.

b. Using the above equation, find the equations for velocity and acceleration.

c.Plot graphs showing the variations of displacement â€˜*xâ€™*, velocity â€˜*vâ€™* and acceleration â€˜*a*â€™ as a function of time.

__SECTION - D__

35. **a. **Explain about Youngâ€™s modulus and give the experimental details to measure Youngâ€™s modulus of a material wire.

b. If an iron wire is stretched by 1%, what is the strain on the wire?

*Or*

**c.** What is the Doppler Effect? Obtain an expression for the apparent frequency heard by the

observer in case the source is moving towards the observer and observer at rest.

d. Discuss harmonics formed in a closed pipe.

36. **a.** Define the adiabatic process. Obtain the expression for work done in an adiabatic process.

b. Why a heat engine with 100% efficiency can never be realized in practice? Explain with the help of Carnotâ€™s engine efficiency expression.

*Or*

**c.** State Bernoulliâ€™s theorem for an incompressible fluid.

**d.** With a neat sketch, explain how one can measure the flow speed of the incompressible fluid. Give an equation for flow speed.

37. **a.** Prove that the path of a projectile is a parabola.

**b.** Give the properties of the dot products and give one example.

*Or*

**a.** The diagrams below show two balls A and B on a horizontal surface. Initially ball B is at rest and ball A is moving with speed *u* along a line joining the centers of the balls.

The mass of the balls is mA and mB.

Using the law of conservation of linear momentum and law of conservation of kinetic energy, obtain the equations for the velocity of ball A and ball B.

*****ALL THE BEST *****

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