Momentum & Impulse — Homi Bhabha Class 9 Physics MCQs with Solutions
Free Homi Bhabha Class 9 Physics Momentum & Impulse MCQs with step-by-step solutions (10 questions). Part of Laws of Motion & Force. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Momentum & Impulse · medium · numerical
The momentum of a body of mass 2 kg moving at 5 m/s is:
A. 2.5 kg·m/s
B. 7 kg·m/s
C. 10 kg·m/s ✓ Correct
D. 25 kg·m/s
Solution: Momentum $p = mv = 2 \times 5 = 10$ kg·m/s.
Q2 — Momentum & Impulse · medium · numerical
A 3 kg body is accelerated from rest to 4 m/s. The impulse given to it is:
A. 12 N·s ✓ Correct
B. 1.33 N·s
C. 7 N·s
D. 0.75 N·s
Solution: Impulse = change in momentum $= m(v - u) = 3(4 - 0) = 12$ N·s.
Q3 — Momentum & Impulse · hard · theory
A cricketer moves his hands backward while catching a fast ball to:
A. decrease the time of impact
B. increase the force on his hands
C. increase the time of impact and so reduce the force ✓ Correct
D. increase the momentum of the ball
Solution: Since impulse (change in momentum) is fixed, increasing the contact time reduces the force ($F = \Delta p / \Delta t$).
Q4 — Momentum & Impulse · hard · numerical
The momentum of a body changes by 20 kg·m/s in 4 s. The average force acting on it is:
A. 5 N ✓ Correct
B. 24 N
C. 80 N
D. 16 N
Solution: $F = \dfrac{\Delta p}{\Delta t} = \dfrac{20}{4} = 5$ N.
Q5 — Momentum & Impulse · hard · numerical
Two bodies have the same momentum. If the mass of the first is 4 times that of the second, the ratio of their velocities (first : second) is:
A. 4 : 1
B. 1 : 4 ✓ Correct
C. 1 : 1
D. 2 : 1
Solution: For equal momentum $m_1 v_1 = m_2 v_2$; with $m_1 = 4m_2$, $v_1 : v_2 = 1 : 4$.
Q6 — Momentum & Impulse · medium · theory
The SI unit of momentum is:
A. kg·m/s²
B. kg·m/s ✓ Correct
C. N·m
D. kg/m·s
Solution: Momentum = mass × velocity, so its unit is kg·m/s (equivalently N·s).
Q7 — Momentum & Impulse · easy · numerical
The momentum of a body of mass 2 kg moving with a velocity of 5 m/s is:
A. 25 kg m/s
B. 10 kg m/s ✓ Correct
C. 2.5 kg m/s
D. 7 kg m/s
Solution: Momentum p = mass × velocity = 2 × 5 = 10 kg m/s.
Q8 — Momentum & Impulse · medium · numerical
A ball of mass 0.5 kg hits a wall horizontally at 4 m/s and rebounds along the same line at 4 m/s. The magnitude of the impulse given to the ball is:
A. 0 kg m/s
B. 4 kg m/s ✓ Correct
C. 8 kg m/s
D. 2 kg m/s
Solution: Impulse equals change in momentum. Taking one direction as positive, the change is 0.5 × (4 - (-4)) = 0.5 × 8 = 4 kg m/s.
Q9 — Momentum & Impulse · medium · theory
A cricketer moves his hands backward while catching a fast ball. This helps him because:
A. it increases the momentum of the ball
B. increasing the time of contact reduces the force needed to stop the ball ✓ Correct
C. decreasing the time of contact reduces the force on the hands
D. it increases the impulse given to the ball
Solution: The change in momentum is fixed, and force = change in momentum ÷ time. Pulling the hands back increases the stopping time, so the force on the hands is smaller and the catch hurts less.
Q10 — Momentum & Impulse · hard · numerical
A constant force of 5 N acts for 4 s on a 2 kg body starting from rest. The final velocity of the body is:
A. 2.5 m/s
B. 10 m/s ✓ Correct
C. 5 m/s
D. 40 m/s
Solution: Impulse = F × t = 5 × 4 = 20 kg m/s equals the change in momentum. Starting from rest, m × v = 20, so v = 20/2 = 10 m/s.