# MCQs for Science Class 9 with Answers Chapter 11 Work and Energy

Students of class 9 Science should refer to MCQ Questions Class 9 Science Work and Energy with answers provided here which is an important chapter in Class 9 Science NCERT textbook. These Multiple Choice Questions have been prepared based on the latest CBSE and NCERT syllabus and examination guidelines for Class 9 Science. The following MCQs can help you to practice and get better marks in the upcoming class 9 Science examination

Question. Choose correct relation :
(A) 1 J = 105 erg
(B) 1 J = 107 erg
(C) 1 J = 103 erg
(D) none of these

B

Question. The kinetic energy of an object is K. If its velocity is doubled than its kinetic energy willbe –
(A) K
(B) 2K
(C)K/2
(D) 4K

D

Q.3 Question.No work is done when –
(A) a nail is plugged in a wooden board
(B) a box is pushed along a horizontal floor
(C) there is no component of force parallel to the direction of motion
(D) there is no component of force perpendicular to the direction of motion

C

Question. A body at rest can have :
(A) speed
(B) velocity
(C) momentum
(D) energy

D

Question. In tug of war work done by winning team is :
(A) zero
(B) positive
(C) negative
(D) none of these

B

Question. One horse power is
(A) 746 W
(B) 550 W
(C) 980 W
(D) 32 W

A

Question. Work done –
(A) is always positive
(B) is always nagative
(C) can be positive, negative or zero
(D) none of these

C

Question. Power of a moving body is stored in the form of-
(A) Work and distance
(B) force and distance
(C) force and velocity
(D) force and time

D

Question. In tug of war work done by loosing team is :
(A) zero
(B) positive
(C) negative
(D) none of these

C

Question. Force F acts on a body such that force F makes an angle  with the horizontal direction and the body is also displaced through a distance S in the horizontal direction, then the work done by the force is –
(A) FS
(B) FS cos 
(C) FS sin 
(D) zero

B

Question. If a stone of mass ‘m’ falls a vertical distance ‘d’ the decrease in gravitational potential energy is-
(A)Mg/d
(B)2Mg2.2
(C) mgd
(D)Mg/ d2

C

Question. Work done by the force of gravity, when a body is lifted to height h above the ground is :
(A) zero
(B) positive
(C) negative
(D) none of these

C

Question. When work is done on a body:
(A) it gains energy
(B) it looses energy
(C) its energy remains constant
(D) none of these

A

Question. Work done upon a body is-
(A) a vector quantity
(B) a scalar quantity
(C) (A) and (B) both are correct
(D) none of these

B

Question. Which of the following is not the unit of power ?
(A) J/s
(B) Watt
(C) kJ/h
(D) kWh

D

Question. Two bodies of mass 1 kg and 4 kg possess equal momentum. The ratio of their K.E.
(A) 4 : 1
(B) 1 : 4
(C) 2 : 1
(D) 1 : 2

A

Question. Which one is not the unit of energy?
(A) kilocalorie
(B) kWh
(C) erg
(D) watt

D

Question. Types of mechanical energy are:
(A) kinetic energy only
(B) potential energy only
(C) kinetic energy and potential energy both
(D) neither kinetic energy nor potential energy

C

Question.Q.17 1 kg mass has K.E. of 1 J when its speed is-
(A) 0.45 ms–1
(B) 1 ms–1
(C) 1.4 ms–1
(D) 4.4 ms–1

C

Question. An object of mass 10 kg falls from height 10 m.. Kinetic energy gained by the body will be approximately equal to-
(A) 1000 J
(B) 500 J
(C) 100 J
(D) None of these

A

Question. The potential energy of a freely falling object decreases continuously. What happens to the loss of potential energy ?
(A) It is continuously converted into sound energy
(B) it is continuously converted into kinetic energy
(C) it is continuously destroyed
(D) None of these

B

Question. Kilowatt is the unit of-
(A) energy
(B) power
(C) force
(D) momentum

B

Question. A raised hammer possess-
(A) kinetic energy only
(B) gravitational potential energy
(C) electrical energy
(D) sound energy

B

Question. A spring is stretched. The potential energy in stretching the spring-
(A) remains the same
(B) increases
(C) decreases
(D) becomes zero

B

Question. An object of mass 1 kg has a P.E. of 1 J relative to the ground when it is at a height of : (g = 9.8 m/s2).
(A) 0.10 m
(B) 10 m
(C) 9.8 m
(D) 32 m

A

Question. Work is product of time and-
(A) energy
(B) power
(C) force
(D) distance

B

Question. The potential energy of a boy is maximum when he is-
(A) standing
(B) sleeping on the ground
(C) sitting on the ground
(D) sitting on chair

A

Question. When a ball is thrown upward, its total energy-
(A) increases
(B) decreases
(C) remains same
(D) none of these

C

Question. The value of g on moon is 1/6th of the value of g on the earth. A man can jump 1.5 m high on the earth. On moon he can jump up to a height of-
(A) 9 m
(B) 7.5 m
(C) 6 m
(D) 4.5 m

A

Question. To lift a 5 kg mass to a certain height, amount of energy spent is 245 J. The mass was raised to a height of-
(A) 15 m
(B) 10 m
(C) 7.5 m
(D) 5 m

D

Question. Work means:
(A) effort
(B) interview
(C) achievement
(D) get-together

C

Question. A young son work quickly for two hours and prepares 16 items in a day. His old father works slowly for eight hours and prepare 24 items a day.
(A) son has more power
(B) son has more energy
(C) both have equal power
(D) both have equal energy

A

Question. Work is done on a body when :
(A) force acts on the body but the body is not displaced
(B) force does not act on the body but it is displaced
(C) force acts on the body in a direction perpendicular to the direction of the displacement of the body
(D) force acts on the body and the body is either displaced in the direction of force or opposite to the direction of force

D

Question. A device which converts mechanical energy into electrical energy is known as-
(A) electric motor
(B) lever
(C) generator
(D) microphone

C

Question. Chlorophyll in the plants convert the light energy into-
(A) heat energy
(B) chemical energy
(C) mechanical energy
(D) electrical energy

B

Question. When you compress a spring you do work on it. The elastic potential energy of the spring-
(A) increases
(B) decreases
(C) disappears
(D) remains constant

A

Question. A weight lifter lifts 240 kg from the ground to a height of 2.5 m in 3 second his power is-
(A) 1960 W
(B) 19.6 W
(C) 1.96 W
(D) 196 W

A

Assertion & Reasoning Based MCQs

(a) Both assertion and reason are true, and reason is correct explanation of the assertion.
(b) Both assertion and reason are true, but reason is not the correct explanation of the assertion.
(c) Assertion is true, but reason is false.
(d) Assertion is false, but reason is true.

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.

A

Question: Assertion :  The change in kinetic energy of a particle is equal to the work done on it by the net force.
Reason : Change in kinetic energy of particle is equal to the work done only in case of a system of one particle.

C

Question: Assertion :  Distance covered in stopping a moving body is equal to kinetic energy/force applied
Reason : Work done in brining a body to just stop must be equal to the kinetic energy of the body.

A

Question: Assertion :  No work is done when a woman carrying a load on her head, walks on a level road with a uniform velocity.
Reason : No work is done if force is perpendicular to the direction of displacement.

A

Question: Assertion :  Work done by or against gravitational force in moving a body from one point to another is independent of the actual path followed between the two points.
Reason : Gravitational forces are conservative forces.

A

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.

C

Question: Assertion :  Work done by the gravitational force through a certain distance is constant irrespective of the fact that the body has a uniform or accelerated motion.
Reason : Gravitational force is a conservative force.

B

Question: Assertion : The kinetic energy, with any reference, must be positive.
Reason : It is because, in the expression for kinetic energy, the velocity appears with power 2 and mass is a scalar quantity.

A

Question: Assertion : Graph between potential energy of a 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.

D

Question: Assertion :  Work done against or by the force of friction in moving a body around a closed loop is zero.
Reason : Work done depends upon the nature of force.

D

Case Based MCQs

Figure shows a watch glass embedded in clay.
A tiny spherical ball is placed at the edge B at a height h above the centre A.

Question: The ball comes to rest because of
(a) frictional force
(b) gravitational force
(c) both (a) and (b)
(d) none of these.

C

Question: The kinetic energy of ball, when it reaches at point A is
(a) zero
(b) maximum
(c) minimum
(d) can’t say.

B

Question: The energy possessed by ball at point C is
(a) potential energy
(b) kinetic energy
(c) both potential and kinetic energy
(d) heat energy.

A

The principle of conservation of energy states that the energy in a system can neither be created nor be destroye(d) It can only be transformed from one form to another, but total energy of the system remains constant.
Conservation of electrical energy to various forms or vice versa along with devices is illustrated in the figure given below.

Question: A battery lights a bul(b) Describe the energy changes involved in the process.
(a) Chemical energy → Light energy → Electrical energy
(b) Electrical energy → Chemical energy → Electrical energy
(c) Chemical energy → Electrical energy → Light energy
(d) None of these.

C

Question: Water stored in a dam possesses
(a) no energy
(b) electrical energy
(c) kinetic energy
(d) potential energy.

D

Question: A body is falling from a height h. After it has fallen a height
h/2 , it will possess
(a) only potential energy
(b) only kinetic energy
(c) half potential and half kinetic energy
(d) more kinetic and less potential energy.

C

Question: Name a machine that transforms muscular energy into useful mechanical work.
(a) Amicrophone
(b) Bicycle
(c) Electric torch
(d) An electric bell

B

An elevator weighing 500 kg is to be lifted up at a constant velocity of 0.4 m s–1. For this purpose a motor of required horse power is used

Question: The acceleration due to gravity in case of upward motion is
(a) 9.8 m s–2
(b) –9.8 m s–2
(c) 8.9 m s–2
(d) –8.9 m s–2

B

Question: The power of motor is
(a) 1940 W
(b) 1950 W
(c) 1960 W
(d) 1970 W

C

Question: The power of motor in hp is
(a) 2.33
(b) 2.43
(c) 2.53
(d) 2.63