Question

A wooden block of mass $20g$ is dropped from the top of the cliff $50m$ high. Simultaneously a bullet of mass $20g$ is fired from the foot of the cliff upwards with a velocity $25m{s}^{-1}$. The bullet and the wooden block will meet each other at a distance from top of the cliff : ($g=10m{s}^{-2}$)

• A. $10m$
• B. $20m$
• C. $30m$
• D. $40m$

Answer 1

The correct option is B $20m$

Let they meet at a distance $h$ from the top and it takes time $t$.



$-h=-\frac{1}{2}g{t}^2$
$h=5t^2\dots \dots \left(i\right)$
$50-h=25t-\frac{1}{2}.g{t}^2$
from equation (1) -
$50-5t^2=25t-5t^2$
$50=25t$
$t=2\text{sec}$
Putting this value of $t=2s$ in equation (i), we get
$h=20m$