Question

Force of $4N$ is applied on a body of mass $20kg.$ The work done in $3^{rd}$ second is

• A. 3 joule
• B. 2 joule
• C. 4 joule
• D. 1 joule

Answer 1

Answer: (B)

$a=\frac{F}{M}=\frac{4}{20}=\frac{1}{5}m/s^2$
$S=\frac{1}{2}a{t}^2=\frac{1}{2}\times \frac{1}{5}\times 3\times 3$
Work done in 3 second
$=4\times \frac{1}{2}\times \frac{1}{5}\times 3\times 3$
$=\frac{18}{5}$ joule
Work done in 2 second
$=4\times \frac{1}{2}\times \frac{1}{5}\times 2\times 2$
$=\frac{8}{5}$ joule
Work done in $3^{\text{rd }}$ second
$=\frac{18}{5}-\frac{8}{5}=\frac{10}{5}=2$ joule