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NDA 2025 GAT · General Knowledge · Motion, Forces and Gravitation · hard

A body of mass 2 kg moving at 3 m/s collides with a stationary body of mass 1 kg and the two stick together. The loss of kinetic energy in the…

Single correct option

A body of mass 2 kg moving at 3 m/s collides with a stationary body of mass 1 kg and the two stick together. The loss of kinetic energy in the collision is
  1. A. 6 J
  2. B. 9 J
  3. C. 3 J
  4. D. zero
Show answer and solution

Answer: (C) 3 J

Momentum is conserved: 2 x 3 = (2 + 1) v, so v = 2 m/s. Initial KE = 1/2 x 2 x 9 = 9 J; final KE = 1/2 x 3 x 4 = 6 J. The loss is 9 - 6 = 3 J. The value 6 J is the final energy, not the loss, and zero would apply only to an elastic collision.
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Original question written in the NDA 2025 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