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JEE Main 2013 · Satellite Energy & Weightlessness

Satellite Energy & Weightlessness question from JEE Main 2013

Q33JEE Main 2013Medium

Satellite Energy & Weightlessness

What is the minimum energy required to launch a satellite of mass mm from the surface of a planet of mass MM and radius RR in a circular orbit at an altitude of 2R2R?

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Answer: (a)

  1. Energy on surface: E1=−GMmRE_1 = -\frac{GMm}{R} (at rest).
  2. In orbit of radius r=R+2R=3Rr = R + 2R = 3R: E2=−GMm2r=−GMm6RE_2 = -\frac{GMm}{2r} = -\frac{GMm}{6R}.
  3. Minimum energy =E2−E1=GMmR−GMm6R=5GMm6R= E_2 - E_1 = \frac{GMm}{R} - \frac{GMm}{6R} = \frac{5GMm}{6R}.
  4. So the answer is (a) 5GmM6R\frac{5GmM}{6R}.
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