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NEET PHYSICSEasy

A ball of mass 0.15 kg is dropped from a height 10 m, strikes the ground, and rebounds to the same height. The magnitude of impulse imparted to the ball is (g=10 m/s2g=10 \text{ m/s}^2) nearly:

A

2.1 kg-m/s

B

1.4 kg-m/s

C

0 kg-m/s

D

4.2 kg-m/s

Step-by-Step Solution

  1. Calculate Impact Velocity: The velocity of the ball just before hitting the ground is given by kinematic equation v=2ghv = \sqrt{2gh}. v=2×10×10=200=102 m/sv = \sqrt{2 \times 10 \times 10} = \sqrt{200} = 10\sqrt{2} \text{ m/s} Taking downward direction as negative, vi=102 m/sv_i = -10\sqrt{2} \text{ m/s}.
  2. Calculate Rebound Velocity: Since the ball rebounds to the same height, the magnitude of velocity remains the same, but the direction is reversed (upward). vf=+102 m/sv_f = +10\sqrt{2} \text{ m/s}
  3. Calculate Impulse: Impulse is defined as the change in momentum (I=Δp=m(vfvi)I = \Delta p = m(v_f - v_i)). I=0.15×[102(102)]I = 0.15 \times [10\sqrt{2} - (-10\sqrt{2})] I=0.15×202I = 0.15 \times 20\sqrt{2} I=32=3×1.4144.24 kg-m/sI = 3\sqrt{2} = 3 \times 1.414 \approx 4.24 \text{ kg-m/s} [Source 60, 61]
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