# Work and Energy MCQ Class 9 Science

Please refer to Chapter 11 Work and Energy MCQ Class 9 Science with answers below. These multiple-choice questions have been prepared based on the latest NCERT book for Class 9 Science. Students should refer to MCQ Questions for Class 9 Science with Answers to score more marks in Grade 9 Science exams. Students should read the chapter Work and Energy and then attempt the following objective questions.

## MCQ Questions Class 9 Science Chapter 11 Work and Energy

The Work and Energy MCQ Class 9 Science provided below covers all important topics given in this chapter. These MCQs will help you to properly prepare for exams.

OBJECTIVE QUESTIONS

Question. A steam engine has an efficiency of 20%. It is given an energy of 1000 cal per min. What is the actual work done by it in calories and in joule?
(a) 100 cal, 800 J
(b) 200 cal, 840 J
(c) 10 cal, 80 J
(d) 100 cal, 100 J

B

Question. Watt second represents the unit of
(a) energy
(b) power
(c) force
(d) none of these

A

Question. When a force retards the motion of a body, the work done is
(a) positive
(b) zero
(c) negative
(d) undefined

C

Question. A body rolls down on inclined plane, it has
(a) only kinetic energy
(b) only potential energy
(c) both kinetic energy and potential energy
(d) neither kinetic energy nor potential energy

C

Question. A ball is thrown upward from a point P, reaches the highest point Q.
(a) kinetic energy at P is equal to kinetic energy at Q
(b) potential energy at P is equal to kinetic energy at Q
(c) kinetic energy at P is equal to potential energy at Q
(d) potential energy at P is equal to potential energy at Q

C

Question. Four forces of equal magnitude are acting on an object as shown in figure. Which of the following forces does the least work?

(a) P
(b) Q
(c) R
(d) S

B

Question. Which one of the following is not the measure of energy?
(a) kWh
(b) erg
(c) Ws
(d) Js

D

Question. If force and displacement of the particle (in direction of force) are doubled, work should be
(a) doubled
(b) 4 times
(c) halved
(d) 1/4 times

B

Question. When the speed of a particle is doubled, the ratio of its kinetic energy to its momentum
(a) remains the same
(b) gets doubled
(c) becomes half
(d) becomes four times

B

Question. A cricket ball is projected vertically upward such that it returns back to the thrower. The variation in kinetic energy with time is best represented by

A

Question. Potential energy of a person is maximum when
(a) person is sitting on a chair
(b) person is standing
(c) person is lying on the ground
(d) person is sitting on the ground

B

Question. A body falling from a height of 10m rebounds from a hard floor. It loses 20% of energy in the impact. What is the height to which it would rise after the impact?
(a) 7m
(b) 5m
(c) 8m
(d) 6m

C

Question. If the angle between force and displacement is θ , then for what value of q is work done zero?
(a) 60c
(b) 45c
(c) 180c
(d) 90c

D

Question. The unit of work is joule. The other physical quantity that has same unit is
(a) power
(b) velocity
(c) energy
(d) force

C

Question. A man carries a suitcase in his hand climbs up the stairs. The work done by the man is
(a) positive
(b) negative
(c) zero
(d) none of the above

A

FILL IN THE BLANK

Question. When angle between force and displacement is obtuse, work done by the force is _____

negative

Question. Work done by a force is maximum when angle between force and displacement is _____

0c

Question. Energy stored in an elongated rubber is _____

Potential energy

Question. The energy possessed by the body due to its _____ is called kinetic energy.

motion

Question. Energy is a _____ quantity.

Scalar

Question. The work done by the external force on a system equals the change in _____ energy.

Total

Question. Watt second is a unit of _____

energy

TRUE/FALSE

Question. Work done by the resultant force is always equal to change in kinetic energy.

True

Question. The total energy of a body in motion is equal to the work it can do in being brought to rest.

False

Question. More work is done in compressing a litre of air than a litre of water from a pressure of one atmosphere to three atmospheres.

True

Question. A light and a heavy body, having equal momenta, have equal kinetic energies.

False

Question. Work is always done on a body when it experiences an increase in energy through a mechanical influence.

True

Question. Work done in the motion of a body over a closed loop is zero for every force in nature.

False

Question. No work is done on a particle which remains at rest.

True

Question. A man rowing a boat up stream is at rest with respect to the shore, is doing no work.

True

MATCHING QUESTIONS

Question.

(c) P-3, Q-1, R-4, S-2

Question.

(a) P-2, Q-4, R-1, S-3

Question.

(a) P-4, Q-1, R-2, S-3

ASSERTION AND REASON

Question. Assertion : The work done during a round trip is always zero.
Reason : No force is required to move a body in its round trip.
Options:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.

C

Question. Assertion : A winded toy car, when placed on floor, starts moving.
Reason : Toy car has kinetic energy stored in it which facilitates its motion.
Options:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.

C

Question. Assertion : Graph between potential energy of spring versus the extension or compression of the spring is a straight line.
Reason : Potential energy of a stretched or compressed spring, is directly proportional to square of extension or compression.
Options:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.

D

Question. Assertion : According to law of conservation of mechanical energy, change in potential energy is equal and opposite to the change in kinetic energy.
Reason : Mechanical energy is not a conserved quantity.
Options:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.

C

Question. Assertion : When the force retards the motion of a body, the work done is zero.
Reason : Work done depends on angle between force and displacement.
Options:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.

D

Question. Assertion : A spring has potential energy, both when it is compressed or stretched.
Reason : In compressing or stretching, work is done on the spring against the restoring force.
Options:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.

A

Question. Assertion : A crane P lifts a car up to a certain height in 1 min. Another crane Q lifts the same car up to the same height in 2 min. Then crane P consumes two times more fuel than crane Q .
Reason : Crane P supplies two times more power than crane Q .
Options:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.

A

Question. Assertion : The kinetic energy, with any reference, must be positive.
Reason : In the expression for kinetic energy, the velocity appears with power 2 and mass is a scalar quantity.
Options:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.

A

Question. Assertion : A crane P lifts a car upto a certain height in 1 min. Another crane Q lifts the same car upto the same height in 2 min. Then crane P consumes two times more fuel than crane Q .
Reason : Crane P supplies two times more power than crane Q .
Options:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.

A

Question. Assertion : Watt hour has units of energy.
Reason : Kilowatt hour (kW h) is the unit of electric power.
Options:
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.