The following 20 Multiple Choice Questions (MCQ) are based on
Chapter 6: How Forces Affect Motion 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
1Which effect can a force produce?
(a) Only a change in colour
(b) A change in motion or shape
(c) Only an increase in mass
(d) A change in time
(b) is correct
A force can start or stop motion, change speed or direction, and deform an object.
2The SI unit of force is:
(a) Joule
(b) Watt
(c) Newton
(d) Pascal
(c) is correct
Force is measured in newtons (N).
3Two horizontal forces of 10 N right and 6 N left act on a block. The net force is:
(a) 16 N right
(b) 4 N right
(c) 4 N left
(d) Zero
(b) is correct
Opposite forces subtract, giving 10 - 6 = 4 N toward the larger force.
4Balanced forces acting on an object produce:
(a) A non-zero net force
(b) Zero net force
(c) Continuous acceleration
(d) A change in mass
(b) is correct
Balanced forces cancel, so they do not change the object's state of motion.
5Which situation definitely involves an unbalanced force?
(a) A book resting on a table
(b) A car accelerating forward
(c) A picture hanging at rest
(d) Two equal teams in a stationary tug-of-war
(b) is correct
Acceleration requires a non-zero net force.
6Friction generally acts:
(a) In the direction of relative sliding
(b) Opposite to relative motion or its tendency
(c) Vertically upward only
(d) Only on stationary objects
(b) is correct
Friction resists relative motion between surfaces in contact.
7Which type of friction usually has the smallest magnitude?
(a) Static friction
(b) Sliding friction
(c) Rolling friction
(d) Limiting friction
(c) is correct
Rolling friction is generally much smaller than sliding friction, which is why wheels are useful.
8Why are grooves made on vehicle tyres?
(a) To reduce all contact
(b) To increase friction and grip
(c) To increase vehicle mass
(d) To eliminate inertia
(b) is correct
Grooves improve traction, especially by helping displace water on wet roads.
9Newton's first law is also called the law of:
(a) Gravitation
(b) Inertia
(c) Conservation of energy
(d) Reflection
(b) is correct
It describes an object's tendency to resist a change in its state of rest or uniform motion.
10When a moving bus stops suddenly, passengers tend to fall forward because of:
(a) Inertia of motion
(b) Inertia of rest
(c) Reduced mass
(d) Action-reaction cancellation
(a) is correct
Their bodies tend to continue moving forward even as the bus stops.
11Which object has greater inertia?
(a) A 1 kg ball
(b) A 10 kg box
(c) Both have equal inertia
(d) Inertia is unrelated to mass
(b) is correct
Mass is a measure of inertia, so the more massive box resists change more strongly.
12Newton's second law for constant mass is expressed as:
(a) F = ma
(b) F = m/a
(c) F = at
(d) F = mv
(a) is correct
The net force equals mass multiplied by acceleration.
13A net force of 12 N acts on a 3 kg object. Its acceleration is:
(a) 4 m/s^2
(b) 9 m/s^2
(c) 15 m/s^2
(d) 36 m/s^2
(a) is correct
Using a = F/m gives 12/3 = 4 m/s^2.
14The same net force acts separately on masses of 2 kg and 4 kg. Which accelerates more?
(a) The 4 kg mass
(b) The 2 kg mass
(c) Both equally
(d) Neither
(b) is correct
For the same force, acceleration is inversely proportional to mass.
15If the net force on an object doubles while its mass remains constant, its acceleration:
(a) Halves
(b) Doubles
(c) Remains unchanged
(d) Becomes zero
(b) is correct
From F = ma, acceleration is directly proportional to net force for fixed mass.
16Newton's third law states that action and reaction forces are:
(a) Equal, opposite and on different objects
(b) Unequal and on one object
(c) Equal and in the same direction
(d) Present only during collisions
(a) is correct
The pair arises from one interaction and acts on the two interacting bodies.
17A canoe moves forward when the paddle pushes water backward due to:
(a) Newton's first law only
(b) Newton's third law
(c) Balanced forces
(d) Absence of friction
(b) is correct
The water exerts an equal and opposite forward force on the paddle and canoe.
18Why do action and reaction forces not cancel each other?
(a) They have different magnitudes
(b) They act at different times
(c) They act on different objects
(d) They point in the same direction
(c) is correct
Only forces acting on the same chosen object can be combined to find its net force.
19A 0.1 kg ball accelerates at 20 m/s^2. The net force is:
(a) 0.5 N
(b) 2 N
(c) 20.1 N
(d) 200 N
(b) is correct
F = ma = 0.1 x 20 = 2 N.
20For a system of interacting objects, internal action-reaction forces:
(a) Cancel when considering the whole system
(b) Always accelerate the centre of mass
(c) Are external forces
(d) Have unequal magnitudes
(a) is correct
Internal forces occur in equal and opposite pairs, leaving external force to determine the system's overall acceleration.
