JEE Main · PhysicsHard

A thin uniform spherical shell of mass and radius is placed in a region of space. A particle of mass is released from rest at a distance from the center of the shell. The time taken by the particle to reach the surface of the shell is given by . If the shell were replaced by a point mass at the center, the time taken to reach the same distance would be . Find the ratio .

  1. A.
  2. B.
  3. C.
  4. D.
Show correct answer & step-by-step solution

Correct answer: A

Solution

  1. For a particle outside a shell or point mass, the gravitational potential is .
  2. The time taken to fall from to depends only on the potential difference and the field in the region .
  3. Since the field for is identical for both the shell and the point mass, the motion is identical until the surface is reached.
  4. Hence the answer is (A).

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