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

Question

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:

Accepted Answer

1.  **Identify Given Values:**
    *   Initial velocity ($v_0$) = 0 (dropped from rest).
    *   Displacement ($y$) = 20 m (taking downward direction as positive).
    *   Acceleration ($a$) = $g$ = 10 m/s².
2.  **Select Kinematic Equation:**
    Use the equation connecting velocity, displacement, and acceleration:
    $$ v^2 = v_0^2 + 2ay $$ 
3.  **Calculation:**
    $$ v^2 = 0^2 + 2(10)(20) $$
    $$ v^2 = 400 $$
    $$ v = \sqrt{400} = 20 	ext{ m/s} $$

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