CBSE Class 11 Physics Work Energy and Power MCQs Set A

Question: According to work-energy theorem, the work done by the net force on a particle is equal to the change in its

• a) kinetic energy
• b) angular momentum
• c) linear momentum
• d) potential energy

Answer: kinetic energy

Question: A light and a heavy body have equal momentum. Which one has greater K.E.?

• a) The lighter body
• b) The heavier body
• c) Both have equal K.E.
• d) Data given is incomplete

Answer: The lighter body

Question: Kinetic energy, with any reference, must be

• a) positive
• b) zero
• c) negative
• d) None of these

Answer: positive

Question: Work done by a conservative force is positive if

• a) P.E. of the body decreases
• b) K.E. of the body increases
• c) K.E. of the body decreases
• d) P.E. of the body increases

Answer: P.E. of the body decreases

Question: The ...X... energy V(x) of the spring is said to be zero when block and spring system is in the ...Y... position. Here, X and Y refer to

• a) potential, equilibrium
• b) kinetic, equilibrium
• c) mechanical, equilibrium
• d) vibrational, left

Answer: potential, equilibrium

Question: Which of the following must be known in order to determine the power output of an automobile?

• a) Work performed and elapsed time of work
• b) Force exerted and distance of motion
• c) Mass and amount of work performed
• d) Final velocity and height

Answer: Work performed and elapsed time of work

Question: A vehicle is moving with a uniform velocity on a smooth horizontal road, then power delivered by its engine must be

• a) increasing
• b) zero
• c) uniform
• d) decreasing

Answer: increasing

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) 1200
• b) 100
• c) 2000
• d) 1000

Answer: 1200

Question: The engine of a vehicle delivers constant power. If the vehicle is moving up the inclined plane then, its velocity

• a) must remain constant
• b) must increase
• c) must decrease
• d) may increase, decrease or remain same

Answer: must remain constant

Question: A body projected vertically from the earth reaches a height equal to earth's radius before returning to the earth. The power exerted by the gravitational force is greatest

• a) at the instant just before the body hits the earth
• b) at the highest position of the body
• c) it remains constant all through
• d) at the instant just after the body is projected

Answer: at the instant just before the body hits the earth

Question: When the force retards the motion of body, the work done is

• a) negative
• b) zero
• c) positive
• d) None of these

Answer: negative

Question: A man pushes a wall and fails to displace it, he does

• a) no work at all
• b) positive but not maximum work
• c) negative work
• d) maximum positive work

Answer: no work at all

Question: A boy carrying a box on his head is walking on a level road from one place to another is doing no work. This statement is

• a) correct
• b) incorrect
• c) partly correct
• d) cannot say

Answer: correct

Question: No work is done if

• a) All of these
• b) force and displacement are mutually perpendicular
• c) force is zero
• d) displacement is zero

Answer: All of these

Question: A particle is taken round a circle by application of force. The work done by the force is

• a) Zero
• b) positive non–zero
• c) negative non–zero
• d) None of these

Answer: Zero

Question:  Assertion : The work done in moving a body over a closed loop is zero for every force in nature.

Reason : Work done depends on nature of force

• a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
• b) Assertion is correct, reason is incorrect
• c) Assertion is incorrect, reason is correct.
• d) Assertion is correct, reason is correct; reason is a correct explanation for assertion

Answer: Assertion is correct, reason is correct; reason is not a correct explanation for assertion

Question: If a motorcyclist skids and stops after covering a distance of 15 m. The stopping force acting on the motorcycle by the road is 100 N, then the work done by the motorcycle on the road is

• a) Zero
• b) 750J
• c) –1500 J
• d) 1500 J

Answer: Zero

Question: A ball moves in a frictionless inclined table without slipping. The work done by the table surface on the ball is

• a) zero
• b) positive
• c) negative
• d) None of these

Answer: zero

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: 18.75 J

Question: A boy pushes a toy box 2.0 m along the floor by means of a force of 10 N directed downward at an angle of 60º to the horizontal. The work done by the boy is

• a) 10 J
• b) 12 J
• c) 8 J
• d) 6 J

Answer: 10 J