Question

A car is going in south with a speed of $5m/s$. To a man sitting in car a bus appears to move towards west with a speed of $2\sqrt{6})m/s$. What is the actual speed of the bus?

• A. $3m/s$
• B. $4m/s$
• C. None of these
• D. $7m/s$

Answer 1

The correct option is D $7m/s$


Given,
${\overrightarrow{v}}_c=-5\hat{j}$
${\overrightarrow{v}}_{bc}=-2\sqrt{6}\hat{i}$
${\overrightarrow{v}}_b={\overrightarrow{v}}_{bc}+{\overrightarrow{v}}_c$
$=-2\sqrt{6\hat{i}}-5\hat{j}$
$\left|\overrightarrow{v_b}\right|=\sqrt{4\times 6+25}=7m/s$
Correct option is (c).