Question

A baseball is popped straight up into the air and stays in air for 6 seconds before touching the ground. Determine the maximum height to which the ball rises? Use g = 10 $m{s}^{-2}$.

• A. 22.5 m
• B. 45 m
• C. 90 m
• D. 180 m

Answer 1

The correct option is B 45 m

Time taken to reach the maximum height = $\frac{6}{2}=3s$
Final velocity, $v=0$, $a=-10m{s}^{-2}$( since moving upwards )
Using the first equation of motion, $v=u+at$,we get,
$0=u-10\times 3$
$\Rightarrow$$u=30m{s}^{-2}$
From second equation of motion, we have ,s = ut + $\frac{1}{2}a{t}^2$
$\Rightarrow$ $s=30\times 3$ – $\frac{1}{2}\times 10\times 3\times 3$
$\Rightarrow$ $s=90–45=45m$