A boy standing at top of a tower of 20 m height drops a stone.assuming g=10 ms⁻²,the velocity with which it hits the ground is

Options

(a) 20 m/s
(b) 40 m/s
(c) 5 m/s
(d) 10 m/s

Correct Answer:

20 m/s

Explanation:

Let, v²=u²+2gh
v= is the final velocity
u= is the initial velocity
g= is the acceleration
h= is the distance
Then, u =0
.·. v²=0²+2gh
v=√2gh
Given, g=10 m/s², h=20 m
.·. v=√2x10x20
v=20 m.