Question

A ball of mass $50g$ is thrown vertically upwards with an initial velocity $20m{s}^{-1}$. Calculate the maximum height reached, if air friction is neglected. Take $g=10m{s}^{-2}$.

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

Answer 1

The correct option is B 20 m

Given, mass of ball, $m=50g=0.05kg$, initial velocity, $u=20m{s}^{-1}$ and acceleration due to gravity, $g=10m{s}^{-2}$.
Let the maximum height reached be $h$.
If air friction is negligible, then
Potential energy at the maximum height $=$ Initial kinetic energy
or, $mgh=\frac{1}{2}m{u}^2$
or, $h=\frac{u^2}{2g}=\frac{{20}^2}{2\times 10}=20m$