Question

A force of 5 N acts on a 15 kg body initially at rest. The work done by the force during the first second of motion of the body is

• A. 5 J
• B. $\frac{5}{6}J$
• C. 6 J
• D. 75 J

Answer 1

The correct option is B

$\frac{5}{6}J$

$W=Fs=F\times \frac{1}{2}a{t}^2[froms=ut+\frac{1}{2}a{t}^2]$
$\Rightarrow W=F[\frac{1}{2}(\frac{F}{m})t^2]=\frac{F^2{t}^2}{2m}=\frac{25\times (1{)}^2}{2\times 15}=\frac{25}{30}=\frac{5}{6}J$