Question

A particle is moving eastward with a velocity $5m/s$, it changes to $5m/s$ northward in $10$ seconds. The average acceleration in this time is:

• A. zero
• B. $\frac{1}{\sqrt{2}}m/s^2$ towards north-west
• C. $\frac{1}{\sqrt{2}}m/s^2$ towards north-east
• D. $\frac{1}{2}m/s^2$ towards north-west

Answer 1

Answer: (B)

$\frac{1}{\sqrt{2}}m/s^2$ towards north-west

$\frac{\Delta \overrightarrow{v}}{\Delta t}=\frac{1}{10}(5\hat{j}-5\hat{i})=\frac{1}{2}(-\hat{i}+\hat{j})(north-west)$

average acceleration $=\frac{1}{2}\sqrt{2}=\frac{1}{\sqrt{2}}m/s^2$