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NDA 2023 GAT · General Knowledge · Work, Energy and Power · medium

A body of mass 2 kg is dropped from a height of 20 m. Taking g = 10 m/s², its kinetic energy just before reaching the ground is

Single correct option

A body of mass 2 kg is dropped from a height of 20 m. Taking g = 10 m/s², its kinetic energy just before reaching the ground is
  1. A. 200 J
  2. B. 400 J
  3. C. 40 J
  4. D. 800 J
Show answer and solution

Answer: (B) 400 J

By conservation of energy the loss of potential energy appears as kinetic energy: K = mgh = 2 × 10 × 20 = 400 J. Using only half of this (200 J) comes from mixing up mgh with ½mv² without the speed.
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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