Question

A body of mass $6$ $kg$ is under a force whic causes displacement in it which is given by
$s=\frac{t^2}{4}m,$ where t is time. The work done by the force in 2 s is

• A. $12J$
• B. $9J$
• C. $6J$
• D. $3J$

Answer 1

The correct option is D $3J$

We have,

$m=6kg$, $s=\frac{t^2}{4}metres$.

After $2$ seconds, $S=\frac{t^2}{4}$ and get the value of $S$ is $1m$

$V=\frac{dS}{dt}$

$v=\frac{t}{2}$

$a=\frac{dv}{dt}$ and hence we get $\frac{1}{2}m/s^2$

$F=ma$ and hence we get $F=6\times \frac{1}{2}$

$F=3N$

$W=F\times S$

$W=3J$