A body is moving with velocity $30 \mathrm{~m} / \mathrm{s}$ towards east. After $10 \mathrm{~s}$ its…
A body is moving with velocity $30 \mathrm{~m} / \mathrm{s}$ towards east. After $10 \mathrm{~s}$ its velocity becomes $40 \mathrm{~m} / \mathrm{s}$ towards north. The average acceleration of the body is
$7 \mathrm{~m} / \mathrm{s}^2$
$\sqrt{7} \mathrm{~m} / \mathrm{s}^2$
$5 \mathrm{~m} / \mathrm{s}^2$
$1 \mathrm{~m} / \mathrm{s}^2$
Solution
$\begin{aligned}
& \text { Average acceleration }=\frac{\text { Change in velocity }}{\text { Total time }} \\
& \qquad \begin{aligned}
a & =\frac{\left|\overrightarrow{\mathbf{v}}_f-\overrightarrow{\mathbf{v}}_i\right|}{\Delta t} \\
& =\frac{\sqrt{30^2+40^2}}{10}=\frac{\sqrt{900+1600}}{10} \\
& =5 \mathrm{~ms}^{-2}
\end{aligned}
\end{aligned}$