### (Update 2021) CBSE Sample Paper for class XI Physics

Time: 3:00 hour/M.M.-70

All questions are compulsory.

Note:-Section A contains 20 questions of 1 mark each. Section B contains 7 questions of 2 marks each. Section C contains 7 questions of 3 marks each. Section D contains 3 questions of 5 marks each.

SECTION-A

1- Which one of the following is not regarded as a fundamental quantity in physics?

i) Length

ii) Mass

iii) Time

iv) weight

2- The error in measurement may occur due to

i) Inexperience of a person

ii) The faulty apparatus

iii) Inappropriate method

iv) Due to all in a, b and c

3- Study of motion of the bodies is known as:

i) Heat

ii) Light

iii) Atomic physics

iv) Mechanics

4- Speed is a _____ quantity.

i) Vector

ii) scalar

iii) both

iv) none of these

5- According to the third law of motion action and reaction:-

i) always act on the same body

ii) always act on different bodies in opposite direction

iii) have same magnitude and direction

iv) Act on either body at normal to each other.

6- An object of mass 2 kg is sliding with a constant velocity of 4 m/s on a frictionless horizontal table. The force required to keep the object moving

i) 32 N

ii) 0 N

iii) 2 N

iv) 8 N

7- The work done by centripetal force is:-

i) smaller to that of centrifugal force

ii) greater than that of centrifugal force

iii) variable in different cases

iv) zero

8- The work given to the machine is called

i) Input

ii) output

iii) velocity ratio

iv) mechanical advantage

9- When the downward acceleration of an elevator is greater than g then the weight of a person becomes:-

i) Positive

ii) negative

iii) zero

iv) none of the above.

10- The moment of linear momentum is called

i) angular momentum

ii) torque

iii) Couple

iv) none of the above

11- Can a quantity have units but still be dimensionless?

12- Distinguish between accuracy and precision.

13- Can a body have a constant speed and still have a varying velocity?

14- What is magnitude and direction of (i^+j^)

15- Heavier bodies need greater initial effort to put them in motion. Why?

16- Sand is spread on tracks covered with snow. Why?

17- Give one example of negative work done?

18- Write formula for kinetic energy and potential energy.

19- Can centre of mass of a body coincide with geometrical centre of the body?

20- Define power.

SECTION- B

21- Let us consider an equationà1/2 mv^{2}= mgh. Check this equation is correct or not.

22- The resistance R=V/I, where V=(100__+__5)volt and I=(10__+__2)A. Find the percentage error in R.

23- State triangle law of vector addition.

24- Define angular velocity and write it’s unit.

25- state second law of motion.

26- State and explain work energy principle.

27- Derive the relation between angular momentum and torque.

SECTION-C

28- Explain the concept of centre of mass of a system.

29- Explain what is meant by potential energy of a spring? Obtain an expression for it and discuss the nature of its variation.

30- A cyclist speeding at 18 kilometer per hour on a level road takes are sharp circular turn of radius 3 meter without reducing the speed. The coefficient of static friction between the tires and road is 0.1 will the cyclist sleep while taking the turn?

31- Two identical 5 kilogram blocks are moving with same speed of 2 meter per second towards each other along a frictionless horizontal surface. The two blocks collide, stick together and come to rest. Calculate work done by (i) external forces and (ii) internal forces.

32- A flywheel of mass 1 metric ton and radius one meter is rotating at the rate of 420 rpm. Find the constant retarding torque required to stop the wheel in 14 rotation assuming mass to be concentrated at the rim of the wheel.

33- An insect trapped in a circular groove of radius 12 centimeter moves along the group steadily and completes 7 revolution in the 100 seconds.(a) what is the angular speed, and the linear speed of the motion?(b) Is the acceleration vector a constant vector ?what is its magnitude?

34- What is centripetal acceleration? Find its magnitude and direction in case of a uniform circular motion of an object.

SECTION-D (Do any three)

35- Why are the curved roads Banked ?obtain an expression for the velocity of the vehicle over the banked road and what is the expression for the optimum speed of the race car to avoid wear and tear on it’s tyres.

36- Discuss elastic collision in one dimension .obtain expressions for velocities of the two bodies after such a collision.

37- Discuss motion of centre of mass and give at least three examples of the motion of centre of mass.

38- Find the angle between force F=(3i^+4j^-5k^) and displacement d=(5i^+4j+3k^) unit. Also, find the projection of F on d.