# A boy standing, at the 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

Q: A boy standing, at the 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

(a) 20 m/s

(b) 40 m/s

(c) 5 m/s

(d) 10 m/s

Ans: (a)

Sol: $\displaystyle v^2 = u^2 + 2 a S$

$\displaystyle v^2 = 0 + 2\times 10 \times 20$

v = 20 m/s