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A body projected vertically from the earth reaches a height equal to earth’s radius

A body projected vertically from the earth reaches a height equal to earth’s radius before returning to 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

Correct Answer:

at the instant just before the body hits the earth

Explanation:

Power exerted by a force is given by P = F.v. When the body is just above the earth’s surface, its velocity is greatest. At this instant, gravitational force is also maximum. Hence, the power exerted by the gravitational force is greatest at the instant just before the body hits the earth.

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