The following 20 Multiple Choice Questions (MCQ) are based on
Chapter 7: Work, Energy, and Simple Machines from the NCERT Class 9
Science textbook Exploration. Each question has four options - select the
best answer and click to check.
Instructions: Read each question carefully. Choose the most
appropriate option from (a), (b), (c), or (d). Click
Show Answer to reveal the correct answer with explanation.
Multiple Choice Questions
1In science, work is done when a force:
(a) Acts without any displacement
(b) Produces displacement with a component along the force
(c) Is merely discussed
(d) Is always vertical
(b) is correct
Work depends on force and displacement in the force's direction.
2For a constant force parallel to displacement, work equals:
(a) Force / displacement
(b) Force x displacement
(c) Mass x acceleration
(d) Power x force
(b) is correct
W = Fs when force and displacement are parallel.
3The SI unit of work and energy is:
(a) Newton
(b) Joule
(c) Watt
(d) Metre per second
(b) is correct
One joule is the work done by a force of one newton through one metre in its direction.
4A 5 N force moves an object 4 m in its direction. Work done is:
(a) 1.25 J
(b) 9 J
(c) 20 J
(d) 25 J
(c) is correct
W = 5 x 4 = 20 J.
5Work done by a force is zero when the displacement is:
(a) Parallel to the force
(b) Opposite to the force
(c) Perpendicular to the force
(d) Twice the force
(c) is correct
A perpendicular force has no component along the displacement.
6A person holds a heavy bag motionless. The mechanical work done on the bag is:
(a) Positive
(b) Negative
(c) Zero
(d) Equal to its mass
(c) is correct
The bag has no displacement, so force times displacement is zero.
7Work done by friction on a sliding object is usually:
(a) Positive
(b) Negative
(c) Zero
(d) Undefined
(b) is correct
Friction points opposite the displacement, so its work is negative.
8The work-energy theorem states that net work equals the change in:
(a) Potential energy only
(b) Kinetic energy
(c) Mass
(d) Power
(b) is correct
Net work done on an object changes its kinetic energy.
9Kinetic energy of a mass m moving with speed v is:
(a) mv
(b) mv^2
(c) 1/2 mv^2
(d) mgh
(c) is correct
Translational kinetic energy is KE = 1/2 mv^2.
10If an object's speed doubles, its kinetic energy becomes:
(a) Twice
(b) Four times
(c) Half
(d) Unchanged
(b) is correct
Kinetic energy depends on the square of speed.
11Gravitational potential energy near Earth's surface is:
(a) mgh
(b) 1/2 mv^2
(c) F/t
(d) mg/h
(a) is correct
Raising mass m through height h stores energy mgh relative to the chosen level.
12Which quantity increases when the same object is raised to a greater height?
(a) Gravitational potential energy
(b) Mass
(c) Power necessarily
(d) Inertia
(a) is correct
For fixed m and g, potential energy is proportional to height.
13During ideal free fall, gravitational potential energy is converted mainly into:
(a) Mass
(b) Kinetic energy
(c) Electric charge
(d) Chemical energy
(b) is correct
As height decreases, speed and kinetic energy increase while total mechanical energy remains constant.
14Mechanical energy is the sum of:
(a) Heat and sound
(b) Kinetic and potential energy
(c) Work and power
(d) Force and displacement
(b) is correct
Mechanical energy combines energy of motion and energy of position or configuration.
15Power is defined as:
(a) Work done per unit time
(b) Force per unit area
(c) Energy x time
(d) Mass per unit volume
(a) is correct
Power measures the rate at which work is done or energy is transferred.
16The SI unit of power is:
(a) Joule
(b) Newton
(c) Watt
(d) Pascal
(c) is correct
One watt equals one joule per second.
17A machine does 600 J of work in 3 s. Its power is:
(a) 200 W
(b) 603 W
(c) 1800 W
(d) 0.005 W
(a) is correct
P = W/t = 600/3 = 200 W.
18A fixed pulley is mainly useful because it:
(a) Always multiplies force
(b) Changes the direction of effort
(c) Eliminates work
(d) Creates energy
(b) is correct
An ideal fixed pulley lets a downward pull lift a load upward, improving convenience.
19An inclined plane reduces the effort needed to raise a load by:
(a) Reducing the height gained
(b) Increasing the distance over which force acts
(c) Creating extra energy
(d) Removing the load's weight
(b) is correct
The same ideal work can be spread over a longer path, requiring a smaller force.
20In a lever, the turning effect of a force about the fulcrum depends on force and:
(a) Perpendicular distance from the fulcrum
(b) Object colour
(c) Power supply
(d) Surface area only
(a) is correct
The moment or torque equals force multiplied by its perpendicular lever arm.
