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Q.
Force of $4\, N$ is applied on a body of mass $20\, kg .$ The work done in $3^{ rd }$ second is
Work, Energy and Power
Solution:
$ 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