Question

A man of mass $m$ is suspended in the air by holding the rope of a stationary balloon of mass M. As the man starts climbing up the rope, the balloon will

• A. $\text{Move upward}$
• B. $\text{Move downward}$
• C. $\text{Remain stationary}$
• D. $\text{Cannot say}$

Answer 1

The correct option is B $\text{Move downward}$

Initially man and balloon are stationary. $\therefore$ Net external force is zero and centre of mass of the system is initially at rest.

Even when man starts moving up, the net external force will remain zero.
$\Rightarrow$ Position of centre of mass will not change. So to have $X_{cm}$ = constant the balloon will move downwards.