# MCQs For NCERT Class 11 Physics Chapter 6 Work, Energy and Power

Please refer to the MCQ Questions for Class 11 Physics Chapter 2 Work, Energy and Power with Answers. The following Work, Energy and Power Class 11 Physics MCQ Questions have been designed based on the latest syllabus and examination pattern for Class 11. Our experts have designed MCQ Questions for Class 11 Physics with Answers for all chapters in your NCERT Class 11 Physics book.

## Work, Energy and Power Class 11 MCQ Questions with Answers

See below Work, Energy and Power Class 11 Physics MCQ Questions, solve the questions and compare your answers with the solutions provided below.

Question. If two particles are brought near one another, the potential energy of the system will
(a) increase
(b) decrease
(c) remains the same
(d) equal to the K.E

A

Question. A ball is allowed to fall from a height of 10 m. If there is 40% loss of energy due to air friction, then velocity of the ball when it hit the ground is
(a) 190m/s
(b) 180m/s
(c) 150m/s
(d) 120m/s

D

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

C

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

C

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

B

Question. A crate is pushed horizontally with 100 N across a 5 m floor. If the frictional force between the crate and the floor is 40 N, then the kinetic energy gained by the crate is
(a) 200 J
(b) 240 J
(c) 250 J
(d) 300 J

D

Question. An engineer claims to have made an engine delivering 10kW power with fuel consumption of 1 g/s. The calorific value of fuel is 2 kcal/g. This claim is
(a) valid
(b) invalid
(c) depends on engine design

B

Question. A force applied by an engine of a train of mass 2.05 × 106 kg changes its velocity from 5m/s to 25 m/s in 5 minutes. The power of the engine is
(a) 1.025 MW
(b) 2.05 MW
(c) 5 MW
(d) 6 MW

B

Question. When a body moves with a constant speed along a circle
(a) no work is done on it
(b) no acceleration is produced in it
(c) its velocity remains constant
(d) no force acts on it.

A

Question. A particle moves in a straight line with retardation proportional to its displacement. Its loss of kinetic energy for any displacement x is proportional to
(a) x2
(b) ex
(c) x
(d) loge x

A

Question. If the extension in a spring is increased to 4 times then the potential energy
(a) remains the same
(b) becomes 4 times
(c) becomes one fourth
(d) becomes 16 times

D

Question. A ball moving with velocity 2 m/s collides head on with another stationary ball of double the mass. If the coefficient of restitution is 0.5, then their velocities (in m/s) after collision will be
(a) 0, 1
(b) 1, 1
(c) 1, 0.5
(d) 0, 2

A

Question. A mass of 20 kg moving with a speed of 10m/s collides with another stationary mass of 5 kg. As a result of the collision, the two masses stick together. The kinetic energy of the composite mass will be
(a) 600
(b) 800
(c) 1000
(d) 1200

B

Question. A body of mass m moving with velocity v collides head on with another body of mass 2m which is initially at rest. The ratio of K. E. of colliding body before and after collision will be
(a) 1 : 1
(b) 2 : 1
(c) 4 : 1
(d) 9 : 1

D

Question. A spherical ball of mass 20 kg is stationary at the top of a hill of height 100 m. It rolls down a smooth surface to the ground, then climbs up another hill of height 30 m and finally  olls down to a horizontal base at a height of 20 m above the ground. The velocity attained by the ball is
(a) 20 m/s
(b) 40 m/s
(c) 10 30 m/s
(d) 10 m/s

B

Question. Which of the following must be known in order to determine the power output of an automobile?
(a) Final velocity and height
(b) Mass and amount of work performed
(c) Force exerted and distance of motion
(d) Work performed and elapsed time of work

D

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

D

Question. How much water, a pump of 2 kW can raise in one minute to a height of 10 m, take g = 10 m/s2?
(a) 1000
(b) 1200
(c) 100
(d) 2000

B

Question. A body of mass 10 kg moves with a velocity v of 2 m/s along a circular path of radius 8 m. The power produced by the body will be
(a) 10 J/s
(b) 98 J/s
(c) 49 J/s
(d) zero

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

B

Question. If two persons A and B take 2 seconds and 4 seconds respectively to lift an object to the same height h, then the ratio of their powers is
(a) 1 : 2
(b) 1 : 1
(c) 2 : 1
(d) l : 3

C

Question. A 10 H.P. motor pumps out water from a well of depth 20 m and fills a water tank of volume 22380 litres at a height of 10 m from the ground. The running time of the motor to fill  he empty water tank is (g = 10ms–2)
(a) 5 minutes
(b) 10 minutes
(c) 15 minutes
(d) 20 minutes

C

Question. If a machine gun fires n bullets per second each with kinetic energy K, then the power of the machine gun is
(a) nK2
(b) K n
(c) n2K
(d) nK

D

Question. A particle of mass 5m at rest suddenly breaks on its own into three fragments. Two fragments of mass m each move along mutually perpendicular direction with speed v each. The energy released during the process is
(a) 3 /5 mv2
(b) 5 /3 mv2
(c) 3/2 mv2
(d) 4 /3mv2

D

Question. A body of mass (4m) is lying in x-y plane at rest.
It suddenly explodes into three pieces. Two pieces, each of mass (m) move perpendicular to each other with equal speeds (v). The total kinetic energy generated due to explosion is
(a) mv2
(b) 3 /2mv2
(c) 2mv2
(d) 4mv

B

Question. A 10 m long iron chain of linear mass density 0.8 kg m–1 is hanging freely from a rigid support. If g = 10 ms–2, then the power required to left the chain upto the point of support  n 10 second
(a) 10 W
(b) 20W
(c) 30 W
(d) 40 W

D

Question. Which one of the following statements is true?
(a) Momentum is conserved in elastic collisions but not in inelastic collisions
(b) Total kinetic energy is conserved in elastic collisions but momentum is not conserved in elastic collisions
(c) Total kinetic energy is not conserved but momentum is conserved in inelastic collisions
(d) Kinetic energy and momentum both are conserved in all types of collisions

C

Question. When after collision the deformation is not relived and the two bodies move together after the collision, it is called
(a) elastic collision
(b) inelastic collision
(c) perfectly inelastic collision
(d) perfectly elastic collision

C

Question. In an inelastic collision, which of the following does not remain conserved?
(a) Momentum
(b) kinetic energy
(c) Total energy
(d) Neither momentum nor kinetic energy

B

Question. The coefficient of restitution e for a perfectly elastic collision is
(a) 1
(b) 0
(c) ¥
(d) –1

A

Question. The coefficient of restitution e for a perfectly inelastic collision is
(a) 1
(b) 0
(c) ¥
(d) –1

B

Question. In case of elastic collision, at the time of impact.
(a) total K.E. of colliding bodies is conserved.
(b) total K.E. of colliding bodies increases
(c) total K.E. of colliding bodies decreases
(d) total momentum of colliding bodies decreases.

C

Question. Assertion : If collision occurs between two elastic bodies their kinetic energy decreases during the time of collision. Reason : During collision intermolecular space decreases and  ence elastic potential energy increases.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.

B

Question. Before a rubber ball bounces off from the floor, the ball is in contact with the floor for a fraction of second. Which of the following statements is correct?
(a) Conservation of energy is not valid during this period
(b) Conservation of energy is valid during this period
(c) As ball is compressed, kinetic energy is converted to compressed potential energy
(d) None of these

B

Question. A particle A suffers an oblique elastic collision with a particle B that is at rest initially. If their masses are the same, then after collision
(a) they will move in opposite directions
(b) A continues to move in the original direction while B remains at rest
(c) they will move in mutually perpendicular directions
(d) A comes to rest and B starts moving in the direction of the original motion of A

C

Question. A metal ball of mass 2 kg moving with a velocity of 36 km/h has a head on collision with a stationary ball of mass 3 kg. If after the collision, the two balls move together, the loss  n kinetic energy due to collision is
(a) 140 J
(b) 100 J
(c) 60 J
(d) 40 J

A

Question. An object of mass 2.0 kg makes an elastic collision with another object of mass M at rest and continues to move in the original direction but with one-fourth of its original speed.  hat is the value of M?
(a) 0.75 kg
(b) 1.0 kg
(c) 1.2 kg
(d) None of these

D

Question. A bullet of mass 20g and moving with 600 m/s collides with a block of mass 4 kg hanging with the string. What is velocity of bullet when it comes out of block, if block rises to  eight 0.2 m after collision ?
(a) 200 m/s
(b) 150 m/s
(c) 400 m/s
(d) 300 m/s

A

Question. A block of mass 0.50 kg is moving with a speed of 2.00 ms–1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is
(a) 0.16 J
(b) 1.00 J
(c) 0.67 J
(d) 0.34 J

C

Question. An electron and a proton are moving under the influence of mutual forces. In calculating the change in the kinetic energy of the system during motion, one ignores the magnetic force of one on another. This is, because
(a) the two magnetic forces are equal and opposite, so they produce no net effect
(b) the magnetic forces do not work on each particle
(c) the magnetic forces do equal and opposite (but nonzero) work on each particle
(d) the magnetic forces are necessarily negligible

B

Question. A proton is kept at rest. A positively charged particle is released from rest at a distance d in its field. Consider two experiments; one in which the charged particle is also a
proton and in another, a positron. In the same time t, the work done on the two moving charged particles is
(a) same as the same force law is involved in the two experiments
(b) less for the case of a positron, as the positron moves away more rapidly and the force on it weakens
(c) more for the case of a positron, as the positron moves away a larger distance
(d) same as the work done by charged particle on the stationary proton

C

Question. A man squatting on the ground gets straight up and stand.
The force of reaction of ground on the man during the process is
(a) constant and equal to mg in magnitude
(b) constant and greater than mg in magnitude
(c) variable but always greater than mg
(d) at first greater than mg and later becomes equal to mg

D

Question. A bicyclist comes to a skidding stop in 10 m. During this process, the force on the bicycle due to the road is 200N and is directly opposed to the motion. The work done by the cycle on the road is
(a) + 2000 J
(b) – 200 J
(c) zero
(d) – 20,000 J

C

Question. A body is falling freely under the action of gravity alone in vaccum. Which of the following quantities remain constant during the fall?
(a) Kinetic energy
(b) Potential energy
(c) Total mechanical energy
(d) Total linear momentum

C

Question. During inelastic collision between two bodies, which of the following quantities always remain conserved?
(a) Total kinetic energy
(b) Total mechanical energy
(c) Total linear momentum
(d) Speed of each body

C

Question. The vector sum of two forces is perpendicular to their vector differences. In that case, the forces
(a) are equal to each other
(b) are equal to each other in magnitude
(c) are not equal to each other in magnitude
(d) cannot be predicted.

B

Question. A particle of mass 10 g moves along a circle of radius 6.4 cm with a constant tangential acceleration. What is the magnitude of this acceleration if the kinetic energy of the particle becomes equal to 8 × 10–4 J by the end of the second revolution after the beginning of the motion?
(a) 0.18 m/s2
(b) 0.2 m/s2
(c) 0.1 m/s2
(d) 0.15 m/s2

D

Question. A bullet of mass 10 g leaves a rifle at an initial velocity of 1000 m/s and strikes the earth at the same level with a velocity of 500 m/s. The work done in joule for overcoming the resistance of air will be
(a) 375
(b) 3750
(c) 5000
(d) 500

B

Question. A body moves a distance of 10 m along a straight line under the action of a 5 N force. If the work done is 25 J, then angle between the force and direction of motion of the body is
(a) 60°
(b) 75°
(c) 30°
(d) 45°