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NDA 2023 GAT · General Knowledge · Motion, Forces and Gravitation · hard

A solid ball of mass 0.5 kg moving at 4 m/s strikes a wall and rebounds with the same speed. The magnitude of the change in its momentum is

Single correct option

A solid ball of mass 0.5 kg moving at 4 m/s strikes a wall and rebounds with the same speed. The magnitude of the change in its momentum is
  1. A. 0
  2. B. 2 kg m/s
  3. C. 8 kg m/s
  4. D. 4 kg m/s
Show answer and solution

Answer: (D) 4 kg m/s

Take the initial momentum as +0.5 × 4 = +2 and the final as −2 kg m/s. The change is 2 − (−2) = 4 kg m/s in magnitude. Writing zero is the trap of comparing the speeds, which are equal, instead of the velocities, which are opposite.
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Original question written in the NDA 2023 GAT pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake