Question

A man in a balloon, throws a stone downwards with a speed of $5\text{m/s}$ with respect to the balloon. The balloon is moving upwards with a constant acceleration of $5{\text{m/s}}^2$. Then velocity of the stone relative to the man after $2\text{seconds}$ is :

• A. $10\text{m/s}$
• B. $30\text{m/s}$
• C. $15\text{m/s}$
• D. $35\text{m/s}$

Answer 1

The correct option is D $35\text{m/s}$

${\overrightarrow{u}}_{SB}=5\text{m/sec}(-\hat{j})$
${\overrightarrow{a}}_{SB}=[10-(-5\left)\right]{\text{m/sec}}^2(-\hat{j})$
${\overrightarrow{a}}_{SB}=15{\text{m/sec}}^2(-\hat{j})$
$v=u+at$
$v=-5-15\times 2=-35\text{m/sec}$
$|\overrightarrow{v}|=35\text{m/sec}$