Question

A stone is dropped from a top of 40 m Height. calculate its speed after 2 seconds.also find the speed with which the stone Strikes the ground.

Answer 1

given :

$u=0$m/sec

$v=?$

$g=9.8m/se{c}^2$

$h=40$ m

1) by using 1st eq. of motion $v=u+gt$

$v=0+9.8\left(2\right)$

$v=19.6$m/sec

2.) using 3rd equation of motion , speed of the stone just before it hits the ground

$v^2=u^2+2gh$

$v^2=0^2+2\times 9.8\times 40$

$v^2=0+19.6\times 40$

$v^2=784$

$v=28$ m/sec