Question

A balloon was moving upwards with a uniform velocity of $10\, m / s$. An object of finite mass is dropped from the balloon when it was at a height of $75\, m$ 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 $10\, m / s ^{2}$ )

• A. 300 m
• B. 200 m
• C. 125 m
• D. 250 m

Answer 1

Answer: (C)

Object is projected as shown so as per motion under gravity
$S=u t+\frac{1}{2} a t^{2}$
$-75=+10 t+\frac{1}{2}(-10) t^{2} \Rightarrow t=5\, \sec$
Object takes $t=5\, s$ to fall on ground
Height of balloon from ground
$H=75+u t$
$=75+10 \times 5=125\, m$