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NDA 2019 GAT · General Knowledge · Motion, Forces and Gravitation · medium

A girl standing on a frictionless surface throws a heavy ball forward. She moves backward because of

Single correct option

A girl standing on a frictionless surface throws a heavy ball forward. She moves backward because of
  1. A. conservation of energy
  2. B. Hooke's law
  3. C. the law of gravitation
  4. D. conservation of linear momentum
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Answer: (D) conservation of linear momentum

The girl and the ball are initially at rest, so their total momentum is zero. When the ball gains forward momentum, she must gain an equal momentum in the opposite direction to keep the total at zero. The same principle explains the recoil of a gun and rocket propulsion.
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Original question written in the NDA 2019 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