Q63 / 270 · NDA 2016 (Phase 1) · General Ability

A body has a free fall from a height of 20 m . After falling through a distance of 5 m , the body would

  • A
    lose one-fourth of its total energy
  • Correct answer
    B
    lose one-fourth of its potential energy
  • C
    gain one-fourth of its potential energy
  • D
    gain three-fourth of its total energy

Solution

According to law of conservation of energy total energy remains conserved. $\text { P.E. }=\mathrm{mgh}=20 \mathrm{mg}$ Loss in potential energy is observed, as $\begin{aligned} & (\text { P.E. })^1=\mathrm{mgh}=5 \mathrm{mg} \\ & (\text { P.E })^1 /(\text { P.E })=5 \mathrm{mg} / 20 \mathrm{mg}=1 / 4 \\ & (\text { P.E. })^1=1 / 4 \text { P.E } \end{aligned}$

Hence, the correct answer is option: 'B'.

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