Question

A stone is dropped from a rising balloon at a height of 300 m above the ground and it reaches the ground in 10 s. The velocity of the balloon when the stone was dropped is :

• A. 19 m $s^{-1}$
• B. 19.6 m $s^{-1}$
• C. 29 m $s^{-1}$
• D. 0 m $s^{-1}$

Answer 1

The correct option is A 19 m $s^{-1}$

Let the velocity of balloon in upward direction be $u$.

Thus initial velocity of stone in the upward direction is also $u$ i.e. $u_1=-u$

Acceleration due to gravity of the stone $a=g=9.8m/s^2$ (downward)

Time taken $t=10$ s

Using $S=u_{1}t+\frac{1}{2}a{t}^2$ (Taking downward direction to be positive)

$\therefore$ $300=-u\left(10\right)+\frac{1}{2}\left(9.8\right)(10{)}^2$

$⟹$ $u=19m/s$