CBSE Class 11 Work Energy and Power Worksheet B

1. When an air bubble rises in water, what happens to its potential energy?

2. What should be the angle between the force and the displacement for maximum and minimum work?

3. What is work done in holding a 15kg suitcase while waiting for a bus for 15 minutes?

4. A light body and a heavy body have same kinetic energy. Which one has greater linear momentum?

5. Can a body have energy without momentum?

6. A particle moves along the x – axis form x = 0 t x = 5m influence of force given by F = 7 – 2x + 3x². Calculate the work done in doing so.

7. A body of mass 3kg makes an elastic collision with another body at rest and continues to move in the original direction with a speed equal to one – third of its original speed. Fine the mass of the second body.

8. Show that for a freely falling body the sum of its kinetic energy and potential energy remains constant at all points during its fall?

9. Ball A of mass m moving with velocity U collides head on with ball B of mass m at rest. If e be the coefficient of restitution then determine the ratio of final velocities of A and B after the collision.

10. If the momentum of the body increases by 20% what will be the increase in the K.E. of the body

Question. In the non-relativistic regime, if the momentum, is increase by 100% , the percentage increase in kinetic energy is
(a) 100
(b) 200
(c) 300
(d) 400

Answer: C

Question. A particle moving in the xy plane undergoes a displacement of s̅ = (2î + 3ĵ) while a constant force F̅ = (5î + 2ĵ) N acts on the particle. The work done by the force F is
(a) 17 joule
(b) 18 joule
(c) 16 joule
(d) 15 joule

Answer: C

Question. A simple pendulum 1 metre long has a bob of 10 kg. If the pendulum swings from a horizontal position, the K.E. of the bob, at the instant it passes through the lowest position of its path is
(a) 89 joule
(b) 95 joule
(c) 98 joule
(d) 85 joule

Answer: C

Question. A particle moves under the effect of a force F = cx from x = 0 to x = x₁, the work done in the process is
(a) cx₁²
(b) 1/2cx₁²
(c) 2cx₁²
(d) zero

Answer: B

Question. A ball is allowed to fall from a height of 10 m. If there is 40% loss of energy due to impact, then after one impact ball will go up to
(a) 10 m
(b) 8 m
(c) 4 m
(d) 6 m

Answer: D

Question. A motor of 100 H.P. moves a load with a uniform speed of 72 km/hr. The forward thrust applied by the engine on the car is
(a) 1111 N
(b) 3550 N
(c) 2222 N
(d) 3730 N

Answer: D

Question. Johnny and his sister Jane race up a hill. Johnny weighs twice as much as jane and takes twice as long as jane to reach the top . Compared to Jane
(a) Johnny did more work and delivered more power.
(b) Johnny did more work and delivered the same amount of power.
(c) Johnny did more work and delivered less power
(d) Johnny did less work and johnny delivered less power.

Answer: B

Question. A bomb of mass 16kg at rest explodes into two pieces of masses 4 kg and 12 kg. The velolcity of the 12 kg mass is 4ms^–1. The kinetic energy of the other mass is
(a) 144 J
(b) 288 J
(c) 192 J
(d) 96 J

Answer: B

Question. Two bodies A and B having masses in the ratio of 3 : 1 possess the same kinetic energy. The ratio of linear momentum of B to A is
(a) 1 : 3
(b) 3 : 1
(c) 1: √3
(d) √3 :1

Answer: C

Question. A ball of mass m moving with a constant velocity strikes against a ball of same mass at rest. If e = coefficient of restitution, then what will be the ratio of velocity of two balls after collision?
(a) 1-e/1+e
(b) e-1/e+1
(c) 1+e/1-e
(d) 2+e/e-1

Answer: A

Question. Calculate the K.E and P.E. of the ball half way up, when a ball of mass 0.1 kg is thrown vertically upwards with an initial speed of 20 ms^–1.
(a) 10 J, 20 J
(b) 10 J, 10 J
(c) 15 J, 8 J
(d) 8 J, 16 J

Answer: B

Question. A spring of force constant 800 N/m has an extension of 5 cm. The work done in extending it from 5 cm to 15 cm is
(a) 16 J
(b) 8 J
(c) 32 J
(d) 24 J.

Answer: B

Question. A spring of spring constant 5 × 103 N/m is stretched initially by 5 cm from the unstretched position. Then the work required to stretch it further by another 5 cm is
(a) 18.75 J
(b) 25.00 J
(c) 6.25 J
(d) 12.50 J

Answer: A

Question. A body of mass m is suspended from a massless spring of natural length l. It stretches the spring through a vertical distance y. The potential energy of the stretched spring is
(a) mg(l + y)
(b) 1/2 mg(l+y)
(c) 1/2mgy
(d) mgy

Answer: C

Question. A ball projected from ground at a certain angle collides a smooth inclined plane at the highest point of its trajectory. If the collision is perfectly inelastic then after the collision, ball will
(a) come to rest
(b) move along the incline
(c) retrace its path.

Answer: B

Question. A mass m₁ moves with a great velocity. It strikes another mass m₂ at rest in a head on collision. It comes back along its path with low speed, after collision. Then
(a) m₁ > m₂
(b) m₁ < m₂
(c) m₁ = m₂
(d) cannot say

Answer: B

Question. A particle describe a horizontal circle of radius 0.5 m with uniform speed. The centripetal force acting is 10 N. The work done in describing a semicircle is
(a) zero
(b) 5 J
(c) 5 p J
(d) 10 p J

Answer: A

Question. A long string is stretched by 2 cm and the potential energy is V. If the spring is stretched by 10 cm, its potential energy will be
(a) V / 25
(b) V/5
(c) 5 V
(d) 25 V

Answer: D

Question. A ball of mass m and a ball B of mass 2m are projected with equal kinetic energies. Then at the highest point of their respective trajectories.
(a) P.E. of A will be more than that of B
(b) P.E of B will be more than that of B
(c) P.E of A will be equal to that of B
(d) can’t be predicted.

Answer: C

Question. A vehicle is moving with a uniform velocity on a smooth horizontal road, then power delivered by its engine must be
(a) uniform
(b) increasing
(c) decreasing
(d) zero

Answer: D

Question. The potential energy of a conservative system is given by U = ay² – by, where y represents the position of the particle and a as well as b are constants. What is the force acting on the system ?
(a) – ay
(b) – by
(c) 2ay – b
(d) b – 2ay

Answer: D

Question. Two bodies of masses 2 m and m have their KE in the ratio 8 : 1. What is the ratio of their momenta ?
(a) 8 : 1
(b) 4 : 1
(c) 2 : 1
(d) 1 : 1

Answer: B

Question. A body accelerates uniformly from rest to a velocity of 1 ms^–1 in 15 seconds. The kinetic energy of the body will be 2/9 J when 't' is equal to [Take mass of body as 1 kg]
(a) 4s
(b) 8s
(c) 10s
(d) 12s

Answer: C

Question. A machine gun fires a bullet of mass 40 g with a velocity 1200 ms^–1. The man holding it can exert a maximum force of 144 N on the gun. How many bullets can he fire per second at the most?
(a) 2
(b) 4
(c) 1
(d) 3

Answer: D

Question. A crane is used to lift 1000 kg of coal from a mine 100 m deep. The time taken by the crane is 1 hour. The efficiency of the crane is 80%. If g = 10 ms^–2, then the power of the crane is
(a) 10⁴ W
(b) 10⁵ W
(c) 10⁴/36 x 8 W
(d) 10⁵/36 x 8 W

Answer: D

Click on link below to download CBSE Class 11 Work Energy and Power Worksheet B.