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Q.
A body of mass $0.5\, kg$ travels on straight line path with velocity $v=\left(3 x^2+4\right) m / s$. The net workdone by the force during its displacement from $x =0$ to $x =2 \,m$ is :
$v _{ i }=3\left(0^2\right)+4=4 \cong x =0$
$ v _{ F }=3(2)^2 \mid 4 \cong x =2$
$=16$
$ W =\Delta K =\frac{1}{2} m \left(16^2-4^2\right)$
$ =\frac{1}{2} \times \frac{1}{2}(256-16) $
$ =\frac{240}{4}=60 \,J $