Question

A person sitting on the top of a tall building drop balls at regular intervals of one second. Find the positions of the $3rd,4^{th}$ and $5^{th}$ ball when the $6^{th}$ ball is being dropped.

Answer 1

For every ball, $u=0,a=g=9.8m/s^2$

$\therefore 4^{th}$ ball moves for $2sec,5^{th}$ ball $1sec$ and $3^{rd}$ ball $3sec$ when $6^{th}$ ball is being dropped.

For $3^{rd}$ ball $t=3sec$

$S_3=ut+\frac{1}{2}a{t}^2$

$=0+1/2\left(9.8\right)3^2$

$=4.9m$ below the top.

For $4^{th}$ ball $t=2sec$

$S_2=0+1/2g{t}^2$

$=1/2\left(9.8\right)2^2$

$=19.6m$ below the top $(u=0)$

For $5^{th}$ ball $t=1sec$

$S_3=ut+1/2a{t}^2$

$=0+1/2\left(9.8\right)t^2$

$=4.98m$ below the top $(u=0)$.