Question

A balloon is moving vertically upward with a velocity of $4m/s$. When it is at a height of $h$, a body is gently released from it. If it reaches the ground in $4s$, the height of the balloon, when the body is released is

• A. $80m$
  
• B. $96m$
• C. $64m$
• D. $78m$

Answer 1

The correct option is C $64m$

As both the balloon and body are moving upwards together.
The particle initially will acquire the velocity of balloon before falling.
Assuming upward direction to be positive.
Initial velocity of balloon is $+4m/s$
By using second equation of motion, we get
$-h=4\times 4-\frac{1}{2}10(4{)}^2$
$\Rightarrow h=64m$