Question

A point mass of $0.5\,kg$ is moving along $x$ -axis as $x=t^{2}+2t,$ where $x$ is in $metre$ and $t$ is in second. Find the work done by all the forces acting on the body during the time interval $\left(\right.0,2\left.\right)$ seconds .

• A. $4J$
• B. $8J$
• C. $16J$
• D. $32J$

Answer 1

Answer: (B)

$v=\frac{d x}{d t}=2t+2$
$v_{2 sec}=2\times 2+2=6msec^{- 1}$
$\&v_{0 sec}=2\times 0+2=2msec^{- 1}$
Now, $W_{all }=\Delta KE=\frac{1}{2}m\left(v_{2}^{2} - v_{0}^{2}\right)$
$=\frac{1}{2}\times \frac{1}{2}\times \left(6^{2} - 2^{2}\right)$
$=\frac{1}{4}\times 32=8J$