Question

A ball is released from the top of a tower of height $hm$. It takes $T$ seconds to reach the ground. What is the position of the ball in $\frac{T}{3}$ second?

• A. $\frac{h}{9}$ metres from the ground
• B. $\frac{7h}{9}$ metres from the ground
• C. $\frac{8h}{9}$ metres from the ground
• D. $\frac{17h}{18}$ metres from the ground

Answer 1

The correct option is C $\frac{8h}{9}$ metres from the ground

Apply second equTION OF MOTION,

$h=ut+\frac{1}{2}g{t}^2$

$h$: height of the tower

$u=0$; Initial velocity

$h=\frac{1}{2}g{T}^2$

In $\frac{T}{3}s$,
$h_1=\frac{1}{2}g(\frac{T}{3}{)}^2$

$\Rightarrow h_1=\frac{1}{9}\left(\frac{1}{2}g{T}^2\right)$

$\Rightarrow h_1=\frac{h}{9}$ from top.

Height from ground-

$h_g=h-h_1=h-\frac{h}{9}$

$\Rightarrow h_g=\frac{8h}{9}$ from ground