Question

One body is dropped, while a second body is thrown downwards with an initial velocity of $1m/s$ simultaneously the separation between these is $18m$ after how much time?

Answer 1

let the required time be $t$.

For freely falling body we have,

$S_1=\frac{1}{2}g{t}^2$

$=\frac{1}{2}\times 10\times t^2$

$=5t^2$

For body thrown downward with $1m/s$,

$S_2=ut+\frac{1}{2}g{t}^2$

$=1\times t+\frac{1}{2}\times 10\times t^2$

$=t+5t^2$

Now $S_2-S_1=18$

$t=18s$