Question 174 of 308

A balloon was moving upwards with a uniform velocity of $10m{s}^{-1}$. An object of finite mass is dropped from the balloon when it was at a height of $75m$ 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 $10m{s}^{-2}$)

A$300m$B$200m$C$125m$D$250m$

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Answer: (C) $125m$

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