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

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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

1. 10.0 m/s
2. 20.0 m/s
3. 40.0 m/s
4. 5.0 m/s

Correct Option: B

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