Question

A stone is dropped from the top of a 40 m high tower. Calculate its speed after 2 s. Also find the speed with which the stone strikes the ground.

Answer 1

Given that,

Height = 40 m

Time t =2 sec

We know that,

$v=u+gt$

$v=0+9.8\times 2$

$v=19.6m/s$

The speed of stone is $19.6m/s$

Now, the speed with which the stone strikes the ground

$v^2=u^2+2gs$

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

$v^2=784$

$v=28m/s$

Hence, the speed with which the stone strikes the ground is $28m/s$