Question

A small platform starts moving from rest from ground in upward direction with uniform acceleration 5 $m{s}^{-2}$. At time $t=2$ s, a stone is projected horizontally in frame of platform with speed 10 $m{s}^{-1}$. The maximum height attained by the stone with respect to the ground is (take g=10 $m/s^2$)

• A. 10 m
• B. 15 m
• C. 25 m
• D. 20 m

Answer 1

Answer: (B)

15 m

$\begin{array}{c}att=2\sec \\ speedofplatform=5\times 2\\ =10m/s\\ and,\\ height=\frac{1}{2}\times 5\times 4=10m\\ Now,\\ max.height=10+\frac{{10}^2}{2\times 10}\\ =10+5\\ =15m\end{array}$

Hence, option $B$ is the correct answer.