A boy standing at the top of a tower of 20m height drops a stone

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

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

20 m/s

Here, u= 0 We have, v² = u² + 2gh
v = √(2gh) ⇒ √(2 x 10 x20)
= 20 m/s

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