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Physics · MOTION IN A STRAIGHT LINE
हिन्दीFor the ball thrown vertically upwards with initial speed \( v_0 = 20.0\text{ m s}^{-1} \) from a height of \( 25.0\text{ m} \) above the ground (taking \( g = 10.0\text{ m s}^{-2} \)), how long after launch does the ball hit the ground?
Correct answer · Option 2
\( 5.0\text{ s} \)
Explanation
Taking launch point as origin, displacement at ground \( y = -25.0\text{ m} \). Using \( y = v_0 t - \frac{1}{2} g t^2 \implies -25 = 20t - 5t^2 \implies 5t^2 - 20t - 25 = 0 \implies t^2 - 4t - 5 = 0 \implies (t - 5)(t + 1) = 0 \). Thus \( t = 5.0\text{ s} \).
