Question:
A balloon was moving upwards with a uniform velocity of $10 \mathrm{~m} / \mathrm{s}$. An object of finite mass is dropped from the balloon when it was at a height of $75 \mathrm{~m}$ from the ground level. The height of the balloon from the ground when object strikes the ground was around :
(takes the value of $g$ as $10 \mathrm{~m} / \mathrm{s}^{2}$ )
Correct Option: , 3
Solution:
Object is projected as shown so as per motion under gravity
$S=u t+\frac{1}{2} a t^{2}$
$-75=+10 t+\frac{1}{2}(-10) t^{2} \Rightarrow t=5 \mathrm{sec}$
Object takes $t=5 \mathrm{~s}$ to fall on ground
Height of balloon from ground
$\mathrm{H}=75+\mathrm{ut}$
$=75+10 \times 5=125 \mathrm{~m}$