A body projected vertically from the earth reaches a height equal to earth's radius before returning ot the earth. The power exerted by the gravitational force is greatest:

Options

A. at the highest position of the body.
B. at the instant just before the body hits the earth.
C. it remains constant all through.
D. at the instant just after the body is projected.

Answer

B

Explanation

Power, `P=F.v`.
Since F and v are maximum when the body is just to hit the each. so power exerted by earth would also be max. at that instant.
Thus correct choice is (b).