Question

A person throws balls into the air vertically upward at regular intervals of time of $1s$. The next ball is thrown when the velocity of the ball thrown earlier becomes zero. The height to which the balls rise is (assume, $g=10m{s}^{-2}$)

• A. $20m$
• B. $5m$
• C. $10m$
• D. $7.5m$

Answer 1

The correct option is B

$5m$

Step 1. Given data

The final velocity of the ball, $v=0m{s}^{-1}$

Time, $t=1s$

$g=10m{s}^{-2}$

Step 2. Finding the initial velocity, $u$

Applying the equation of motion

$v=u+gt$

$0=u+\left(-10\times 1\right)$ [$g=-10m{s}^{-2}$ as the ball is thrown upward]

$u=10m{s}^{-1}$

Step 3. Finding the height to which the ball rises, $H$

By applying the formula of height,

$H=\frac{u^2}{2g}$

$H=\frac{10\times 10}{2\times 10}$

$H=5m$

Hence, the correct option is $\left(B\right)$.