Work Energy and Simple Machines Class 9 MCQ Questions Science Chapter 7

These Class 9 Science MCQ and Class 9 Science Exploration Chapter 7 MCQ Online Test with Answers Work Energy and Simple Machines focus on both theory and practical applications.

Class 9 Science Chapter 6 Work Energy and Simple Machines MCQ

Work Energy and Simple Machines MCQ

Class 9 Science Chapter 7 MCQ Online Test

Question 1.
A force of 10 N acts on a body, but the body does not move. The work done is
(a) 100 J
(b) 10 J
(c) 0 J
(d) Cannot be determined.
Answer:
(c) 0 J

Question 2.
A body is moving in a circular path under centripetal force. The work done by this force is
(a) positive
(b) negative
(c) zero
(d) infinite.
Answer:
(c) zero

Question 3.
If the velocity of a body is doubled, its kinetic energy becomes
(a) doubled
(b) halved
(c) four times
(d) unchanged.
Answer:
(c) four times

Question 4.
A body of mass m is lifted to height h and then dropped. Ignoring air resistance, its velocity just before hitting the ground depends on:
(a) mass only
(b) height only
(c) both mass and height
(d) acceleration only.
Answer:
(b) height only

Question 5.
Two objects of masses 2 kg and 4 kg are dropped from the same height. Neglecting air resistance, which statement is correct?
(a) Heavier object reaches first
(b) Lighter object reaches first
(c) Both reach at the same time with same velocity
(d) Both reach at the same time but with different velocities.
Answer:
(c) Both reach at the same time with same velocity

Question 6.
A machine has mechanical advantage of 4 and efficiency 50%. If the load is 200 N, the effort applied is
(a) 25 N
(b) 50 N
(c) 100 N
(d) 800 N
Answer:
(b) 50 N

Question 7.
A person pushes a box with a force F at an angle θ to the horizontal, but the box moves horizontally. The work done is given by
(a) F sin θ × s
(b) F cos θ × s
(c) F × S
(d) F tan θ × s
Answer:
(b) F cos θ × s

Question 8.
In a lever, if the effort arm is three times the load arm, the mechanical advantage is
(a) 1/3
(b) 1
(c) 3
(d) 9
Answer:
(c) 3

Question 9.
A ball is thrown vertically upward. At the highest point,
(a) kinetic energy is maximum
(b) potential energy is zero
(c) kinetic energy is zero, and potential energy is maximum
(d) both kinetic and potential energy are zero.
Answer:
(c) kinetic energy is zero, and potential energy is maximum

Question 10.
A machine does 500 J of useful work using 800 J of input energy. Its efficiency is:
(a) 62.5%
(b) 80%
(c) 50%
(d) 40%
Answer:
(a) 62.5%

Question 11.
The unit of work is joule. The other physical quantity that has same unit is
(a) power
(b) velocity
(c) energy
(d) force.
Answer:
(a) power

Question 12.
The spring will have maximum potential energy when
(a) it is pulled out
(b) it is compressed
(c) both (a) and (b)
(d) neither (a) nor (b).
Answer:
(a) it is pulled out

Question 13.
Water stored in a dam possesses
(a) no energy
(b) electrical energy
(c) kinetic energy
(d) potential energy
Answer:
(c) kinetic energy

Question 14.
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
Answer:
(c) half potential and half kinetic energy

Question 15.
Which of these is an example of scientific work done?
(a) Standing with a load of 2 kg on the head for 5 minutes
(b) Playing video games when sitting on a sofa
(c) Sitting on a chair and reading a book
(d) Climbing stairs of a bridge
Answer:
(b) Playing video games when sitting on a sofa

Question 16.
Which class of lever has the load between effort and fulcrum?
(a) First class
(b) Second class
(c) Third class
(d) Fourth class
Answer:
(b) Second class

Question 17.
A boy pushes a lawn mower to a total distance of 125 m over the grass with a force of 60 N directed horizontally. How much work is done in joules by the boy?
(a) +7500
(b) -7500
(c) +2.03
(d) -2.03
Answer:
(a) +7500

Question 18.
An object of mass 25 kg is at a height of 8 m above the ground. How much work is this object capable of doing? (Given g = 9.8 ms^-2.)
(a) 1960 J
(b) 2000 J
(c) 9600 J
(d) 20000 J
Answer:
(a) 1960 J

Question 19.
The kinetic energy of an object weighing 10 kg moving with a velocity of 5 m/s is 125J. What is the maximum amount of work that can be done by the object?
(a) 5 J
(b) 10 J
(c) 125 J
(d) 1250 J
Answer:
(c) 125 J

Question 20.
Which of the following is NOT a simple machine?
(a) Lever
(b) Pulley
(c) Screw
(d) Engine
Answer:
(b) Pulley

Question 21.
A car weighing 500 kg is moving with a uniform velocity of 15 m/s. What is the kinetic energy possessed by the car?
(a) 56.250 kJ
(b) 12.500 kJ
(c) 56250 kJ
(d) 12500 kJ
Answer:
(a) 56.250 kJ

Question 22.
A man of mass is 60 kg climbs up 50 steps of a stair in 2 minutes. If each step is 20 cm high, calculate the power used in climbing the stairs. (Given g = 10 m/s²)
(a) 50 W
(b) 250 W
(c) 3000 W
(d) 6000 W
Answer:
(a) 50 W

Question 23.
A machine do a work of 100 joule in 20 seconds. What is its power?
(a) 20 watt
(b) 80 watt
(c) 5 watt
(d) 2000 watt
Answer:
(c) 5 watt

Question 24.
The work done by the losing team in a tug of war is

(a) zero
(b) positive
(c) negative
(d) none of these.
Answer:
(c) negative

Work Energy and Simple Machines Class 9 Assertion and Reason Questions

Directions (Q. No. 1 to 10): Each question below consists of an Assertion (A) and a Reason (R). Use the following key: (a) Both A and R are true, but R is not the correct explanation of A.
(b) Both A and R are true, and R is the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Question 1.
Assertion (A): A person pushing a wall does no work scientifically.
Reason (R): Work requires both force and displacement in the direction of force.
Answer:
(b) Both A and R are true, and R is the correct explanation of A.

Question 2.
Assertion (A): Scissors are a Class I lever.
Reason (R): In scissors, the effort is applied in the middle between fulcrum and load.
Answer:
(c) A is true but R is false.

Question 3.
Assertion (A): Doubling the height of an object doubles its gravitational potential energy.
Reason (R): Gravitational P.E. = mgh, which is directly proportional to height h.
Answer:
(b) Both A and R are true, and R is the correct explanation of A.

Question 4.
Assertion (A): A real machine can have efficiency greater than 100%.
Reason (R): Friction in real machines always causes energy loss.
Answer:
(d) A is false but R is true.

Question 5.
Assertion (A): In a second-class lever, load lies between fulcrum and effort.
Reason (R): Second-class levers always have mechanical advantage greater than 1.
Answer:
(b) Both A and R are true, and R is the correct explanation of A.

Question 6.
Assertion (A): The potential energy possessed by the object is the energy present in it by virtue of its position or configuration.
Reason (R): The stretched rubber band posses potential energy.
Answer:
(a) Both A and R are true, but R is not the correct explanation of A.

Question 7.
Assertion (A): The kinetic energy is always positive.
Reason (R): In the kinetic energy formula, velocity has power 2, and mass is a scalar quantity.
Answer:
(b) Both A and R are true, and R is the correct explanation of A.

Question 8.
Assertion (A): Watt hour is a unit of energy.
Reason (R): Kilowatt hour (kWh) is a unit of electric power.
Answer:
(c) A is true but R is false.

Question 9.
Assertion (A): ‘A’ is a light body and ‘B’ is a heavy body having same momentum. Also, they have same kinetic energy.
Reason (R): Kinetic energy depends on mass of the body.
Answer:
(d) A is false but R is true.

Question 10.
Assertion (A): A spring has potential energy in both case, when it is compressed or stretched.
Reason (R): In compressing or stretching, work is done on the spring against the restoring force.
Answer:
(b) Both A and R are true, and R is the correct explanation of A.

Work Energy and Simple Machines Class 9 Fill in the Blanks

1. Work done is the product of force and the ……………………….. .
Answer:
displacement

2. The SI unit of work and energy is ……………………….. .
Answer:
joule (J)

3. Power is defined as the rate of doing ……………………… .
Answer:
work

4. A lever with the load between the fulcrum and effort is a Class lever …………………… .
Answer:
II

5. When only conservative forces act, mechanical energy is ……………………….. .
Answer:
conserved.

Work Energy and Simple Machines Class 9 True or False

1. Work is a vector quantity.
Answer:
False

2. A movable pulley has a mechanical advantage of 2.
Answer:
True

3. Potential energy of an object increases as it falls from a height.
Answer:
False

4. Power of an engine can be expressed as P = Fv.
Answer:
True

5. An ideal machine has 100% efficiency.
Answer:
True

Work Energy and Simple Machines Class 9 Match the Following

Question 1.
Match the items in column A with those in column B.

Column A	Column B
(i) Work done = 0	(p) Power (force – displacement)
(ii) Rate of doing work	(q) Inclined plane
(iii) Sloping surface to raise objects	(r) Joule
(iv) SI unit of energy	(s) Zero work

Answer:
(i) – (s), (ii) – (p), (iii) – (q), (iv) – (r)

Column A	Column B
(i) Work done = 0	(s) Zero work
(ii) Rate of doing work	(p) Power (force – displacement)
(iii) Sloping surface to raise objects	(q) Inclined plane
(iv) SI unit of energy	(r) Joule

Question 2.
Match the types of work with their characteristics:

Column A	Column B
(i) Positive Work	(p) Work involving machines or tools
(ii) Negative Work	(q) No displacement despite force applied
(iii) Zero Work	(r) Force opposite to displacement
(iv) Mechanical	(s) Force and displacement Work in same direction

(a) (i) – (p), (ii) – (q), (iii) – (r), (iv) – (s)
(b) (i) – (s), (ii) – (r), (iii) – (q), (iv) – (p)
(c) (i) – (r), (ii) – (s), (iii) – (p), (iv) – (q)
(d) (i) – (q), (ii) – (p), (iii) – (s), (iv) – (r)
Answer:
(b) (i) – (s), (ii) – (r), (iii) – (q), (iv) – (p)

Column A	Column B
(i) Positive Work	(s) Force and displacement Work in same direction
(ii) Negative Work	(r) Force opposite to displacement
(iii) Zero Work	(q) No displacement despite force applied
(iv) Mechanical	(p) Work involving machines or tools

Question 3.
Match the energy conversions with their applications:

Column A	Column B
(i) Electrical to Mechanical	(p) Battery in a mobile phone
(ii) Chemical to Electrical	(q) Solar panels
(iii) Solar to Electrical	(r) Loudspeaker
(iv) Mechanical to Sound	(s) Electric fan

(a) (i) – (p), (ii) – (q), (iii) – (r), (iv) – (s)
(b) (i) – (s), (ii) – (p), (iii) – (q), (iv) – (r)
(c) (i) – (q), (ii) – (r), (iii) – (s), (iv) – (p)
(d) (i) – (r), (ii) – (s), (iii) – (p), (iv) – (q)
Answer:
(b) (i) – (s), (ii) – (p), (iii) – (q), (iv) – (r)

Column A	Column B
(i) Electrical to Mechanical	(s) Electric fan
(ii) Chemical to Electrical	(p) Battery in a mobile phone
(iii) Solar to Electrical	(q) Solar panels
(iv) Mechanical to Sound	(r) Loudspeaker

Question 4.
Match the types of power with their descriptions:

Column A	Column B
(i) Mechanical Power	(p) Power obtained from sunlight
(ii) Electrical Power	(q) Rate of doing work using a machine
(iii) Solar Power	(r) A unit of power used for engines
(iv) Horsepower	(s) Rate at which electrical energy is transferred

(a) (i) – (p), (ii) – (q), (iii) – (r), (iv)-(s)
(b) (i) – (s), (ii) – (r), (iii) – (q), (iv) – (p)
(c) (i) – (q), (ii) – (s), (iii) – (p), (iv) – (r)
(d) (i) – (r), (i1) – (p), (iii) – (s), (iv) – (q)
Answer:
(c) (i) – (q), (ii) – (s), (iii) – (p), (iv) – (r)

Column A	Column B
(i) Mechanical Power	(q) Rate of doing work using a machine
(ii) Electrical Power	(s) Rate at which electrical energy is transferred
(iii) Solar Power	(p) Power obtained from sunlight
(iv) Horsepower	(r) A unit of power used for engines

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