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MHT CET 2021 (21 Sep, Shift 1) · Escape Velocity

Escape Velocity question from MHT CET 2021 (21 Sep, Shift 1)

Q50MHT CET 2021 · 21 SEP · SHIFT 1Medium

Escape Velocity

A particle of mass 'mm' is kept at rest at a height 3R3R from the surface of earth, where 'RR' is radius of earth and 'MM' is the mass of earth. The minimum speed with which it should be projected, so that it does not return back is ( g=g = acceleration due to gravity on the earth's surface)

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Answer: (a)

  1. Height 3R3R means distance r=4Rr = 4R from the centre.
  2. Escape speed there: v=2GMr=2GM4Rv = \sqrt{\frac{2GM}{r}} = \sqrt{\frac{2GM}{4R}}.
  3. v=[GM2R]1/2v = \left[\frac{GM}{2R}\right]^{1/2}.
  4. So the answer is (a).
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