Question

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 :

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

Answer 1

The correct option is B at the instant just before the body hits the earth

$Power,$ $P$ $=$$\overrightarrow{F}$.$\overrightarrow{v}$ $=$ $Fv$ $cos$$\theta$

$Just$ $before$ $hitting$ $the$ $earth$ $\theta$ $=$ $0°.$ $Hence,$ $the$ $power$ $exerted$ $by$ $the$ $gravitational$ $force$ $is$ $greatest$ $at$ $the$ $instant$ $just$ $before$ $the$ $body$ $hits$ $the$ $earth.$