Question

Balls are thrown vertically upward in such a way that the next ball is thrown when the previous one is at the maximum height. If the maximum height is $5\text{m}$, the number of balls thrown per minute will be

• A. $40$
• B. $50$
• C. $60$
• D. $120$

Answer 1

The correct option is C $60$

As we know that,
$H_{max}=\frac{u^2}{2g}$
$\Rightarrow u=\sqrt{2g{H}_{max}}=\sqrt{2\times 10\times 5}$
$\Rightarrow u=10\text{m/s}$
Now, time to reach $H_{max}$ by each ball is
$t=\frac{u}{g}=\frac{10}{10}=1\text{sec}$
Thus, balls thrown in $1\text{min}$ will be $60$.