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NEET 2021 · Conservation of Energy

Conservation of Energy question from NEET 2021

Q23NEET 2021Medium

Conservation of Energy

A particle is released from height S from the surface of the Earth. At a certain height its kinetic energy is three times its potential energy. The height from the surface of earth and the speed of the particle at that instant are respectively -

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Answer: (a)

  1. Total energy mgS=K+UmgS = K + U and K=3UK = 3U, so 4U=mgS4U = mgS.
  2. mgh=mgS4⇒h=S4mgh = \frac{mgS}{4} \Rightarrow h = \frac{S}{4}
  3. Fall distance =3S4= \frac{3S}{4}: v=2g⋅3S4=3gS2v = \sqrt{2g \cdot \frac{3S}{4}} = \sqrt{\frac{3gS}{2}}
  4. So the answer is (a) S4,3gS2\frac{S}{4}, \sqrt{\frac{3gS}{2}}.
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