Impulse & Impulse-Momentum Theorem — JEE Main Physics MCQs with Solutions
Free JEE Main Physics Impulse & Impulse-Momentum Theorem MCQs with step-by-step solutions (8 questions). Part of Centre of Mass, Momentum & Collisions. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Impulse & Impulse-Momentum Theorem · easy · theory
Impulse of a force equals:
A. The change in kinetic energy
B. The change in momentum it produces (∫F dt = Δp) ✓ Correct
C. Force × displacement
D. Power × time
Solution: J⃗ = ∫F⃗dt = Δp⃗; its unit N·s ≡ kg·m/s. Graphically, the area under the F–t curve.
Q2 — Impulse & Impulse-Momentum Theorem · medium · theory
A cricketer draws his hands back while catching a fast ball. This reduces the force on his hands because:
A. The same Δp is spread over a longer time, so F_avg = Δp/Δt drops ✓ Correct
B. The ball does less work
C. The impulse becomes smaller
D. The ball's momentum change is reduced
Solution: Δp is fixed by the catch; lengthening Δt lowers the average force. Same physics as airbags and shock absorbers.
Q3 — Impulse & Impulse-Momentum Theorem · easy · numerical
A 0.15 kg cricket ball arrives at 20 m/s and is caught and stopped in 0.1 s. The average force on the hands is:
A. 30 N ✓ Correct
B. 300 N
C. 15 N
D. 3 N
Solution: F = Δp/Δt = 0.15×20/0.1 = 30 N.
Q4 — Impulse & Impulse-Momentum Theorem · medium · numerical
A 0.5 kg ball hits a wall normally at 12 m/s and rebounds at 8 m/s. The impulse on the ball is:
A. 10 N·s ✓ Correct
B. 2 N·s
C. 6 N·s
D. 4 N·s
Solution: Taking rebound positive: J = 0.5(8 − (−12)) = 0.5×20 = 10 N·s. Trap: speeds ADD when direction reverses.
Q5 — Impulse & Impulse-Momentum Theorem · hard · numerical
A force acting on a 2 kg body varies as a triangle on the F–t graph: rising 0→20 N over 0→2 s, falling to 0 at t = 4 s. The body starts at rest; its final speed is:
A. 40 m/s
B. 80 m/s
C. 10 m/s
D. 20 m/s ✓ Correct
Solution: Impulse = area = ½×4×20 = 40 N·s = mv ⇒ v = 20 m/s.
Q6 — Impulse & Impulse-Momentum Theorem · medium · numerical
A hammer of mass 1 kg moving at 10 m/s strikes a nail and stops in 0.01 s. The average force on the nail is:
A. 1000 N ✓ Correct
B. 10000 N
C. 100 N
D. 10 N
Solution: F = mv/t = 10/0.01 = 1000 N — why hammers work.
Q7 — Impulse & Impulse-Momentum Theorem · hard · numerical
A 0.2 kg ball strikes a smooth floor at 10 m/s, at 37° to the VERTICAL, and rebounds symmetrically at the same speed and angle (sin37° = 0.6, cos37° = 0.8). The impulse delivered by the floor is:
A. 1.2 N·s upward
B. 4 N·s
C. 3.2 N·s, vertically upward ✓ Correct
D. 2.4 N·s, horizontal
Solution: Only the vertical component reverses: J = 2mv cos37° = 2×0.2×10×0.8 = 3.2 N·s upward. Trap: the horizontal momentum is unchanged on a smooth floor.
Q8 — Impulse & Impulse-Momentum Theorem · medium · numerical
The momentum of a body changes as p = 4t² (kg·m/s). The force acting on it at t = 2 s is:
A. 16 N ✓ Correct
B. 32 N
C. 4 N
D. 8 N
Solution: F = dp/dt = 8t = 16 N at t = 2 s.