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Force and Laws of Motion — Class 9 CBSE Science MCQs with Solutions
Free Class 9 CBSE Science Force and Laws of Motion MCQs with step-by-step solutions. Practise online on Prepizo — no login needed.
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Sample questions with solutions
Q1 — easy
Inherent property of a body to resist any change in its state of rest or uniform motion is:
A. Momentum
B. Inertia ✓ Correct
C. Force
D. Impulse
Solution: Inertia is the natural resistance to state change.
Q2 — easy
Inertia of a body is directly proportional to its:
A. Velocity
B. Mass ✓ Correct
C. Area
D. Volume
Solution: Mass is a direct quantitative measure of inertia.
Q3 — easy
Newton’s First Law of Motion is also known as the Law of:
A. Acceleration
B. Inertia ✓ Correct
C. Action-Reaction
D. Gravitation
Solution: First law formalizes Galilean inertia.
Q4 — easy
Newton’s Second Law of Motion states that rate of change of momentum is proportional to:
A. Velocity
B. Applied unbalanced force ✓ Correct
C. Mass
D. Distance
Solution: F = dp/dt = m·a.
Q5 — easy
Newton’s Third Law of Motion states that to every action there is an equal and opposite:
A. Displacement
B. Reaction ✓ Correct
C. Friction
D. Momentum
Solution: Action and reaction forces are equal in magnitude and opposite in direction.
Q6 — easy
Recoil of a gun when a bullet is fired demonstrates:
A. Newton’s First Law
B. Law of Conservation of Momentum (and Third Law) ✓ Correct
C. Gravity
D. Centripetal force
Solution: Conservation of momentum: gun recoils backward as bullet fires forward.
Q7 — easy
A force of 20 N acts on a body of mass 4 kg. Produced acceleration is:
A. 80 m/s²
B. 5 m/s² ✓ Correct
C. 0.2 m/s²
D. 16 m/s²
Solution: a = F / m = 20 / 4 = 5 m/s².
Q8 — easy
When a moving bus stops suddenly, passengers lurch forward due to:
A. Inertia of rest
B. Inertia of motion ✓ Correct
C. Gravitational pull
D. Friction
Solution: Upper body remains in motion due to inertia.
Q9 — easy
Dust particles fly off a carpet when beaten with a stick due to:
A. Inertia of rest ✓ Correct
B. Inertia of motion
C. Gravity
D. Friction
Solution: Carpet moves, while dust particles remain at rest due to inertia.
Q10 — easy
Total momentum of an isolated system before and after collision remains:
A. Zero
B. Conserved (Constant) ✓ Correct
C. Doubled
D. Variable
Solution: Law of Conservation of Linear Momentum.
Q11 — easy
Action and reaction forces always act on:
A. Same body in same direction
B. Two different bodies in opposite directions ✓ Correct
C. Same body in opposite directions
D. Earth only
Solution: Action-reaction pairs act on different objects simultaneously.
Q12 — medium
Linear momentum (p) of a body of mass m moving with velocity v is given by:
A. p = m / v
B. p = m × v ✓ Correct
C. p = ½mv²
D. p = m × a
Solution: Momentum p = mass × velocity.
Q13 — medium
SI unit of linear momentum is:
A. kg·m/s²
B. kg·m/s ✓ Correct
C. N·m
D. J·s
Solution: Mass (kg) × Velocity (m/s) = kg·m/s.
Q14 — medium
Mathematical formula derived from Newton’s Second Law is:
A. F = m × a ✓ Correct
B. F = m / a
C. F = v / t
D. F = p × t
Solution: Force = Mass × Acceleration.
Q15 — medium
SI unit of force is Newton (N), which is equivalent to:
A. 1 kg·m/s
B. 1 kg·m/s² ✓ Correct
C. 1 g·cm/s²
D. 1 J/s
Solution: 1 N = 1 kg × 1 m/s².