Question

A skydiver with mass of $60kg$ is moving at a constant speed of $20m{s}^{-1}$ . Rate of work done by gravity is _____. Take $g=10m{s}^{-2}$

• A. $6kW$
• B. $8kW$
• C. $12kW$
• D. $6kW$

Answer 1

The correct option is C $12kW$

Given:
Mass of skydiver $m=60kg$,
Constant velocity = $v$ = $20m{s}^{-1}$
Acceleration due to gravity $g=10m{s}^{-2}$
Rate of work done by gravity = $\frac{workdone}{time}$
Force applied by gravity $F=mg=60\times 10=600N$.
Let the skydiver travel $xmetres$ in $tseconds.$
Work done in $tseconds$ = Force $\times$ Displacement
$=(60\times 10\times x)J$
So, power $=\frac{(60\times 10\times x)}{t}$
= $60\times 10\times \frac{x}{t}$
= $60\times 10\times v$
= $60\times 10\times 20$
= $12000W$
= $12kW$