Question

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

• 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

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

After $\frac{T}{3}$seconds,the position of ball,

$h^{\prime }=0+\frac{1}{2}g{\left(\frac{T}{3}\right)}^2=\frac{1}{2}\times \frac{g}{9}\times T^2$

$h^{\prime }=\frac{1}{2}\times \frac{g}{9}\times T^2=\frac{h}{9}m$ from top.

$\therefore$Position of ball from ground$=h-\frac{h}{9}=\frac{8h}{9}m.$