A boy is standing on top of a tower of height | vedclass

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(B) Given,the sound of the ball hitting the ground is heard $5.25 \, s$ after the ball is thrown.The sound of the ball hitting the ground travels from

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$8$

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(B) Given,the sound of the ball hitting the ground is heard $5.25 \, s$ after the ball is thrown.The sound of the ball hitting the ground travels from the ground to the top of the tower. The time taken for the sound to reach the top of the tower is:$t_1 = \frac{D}{v_{sound}} = \frac{85}{340} = 0.25 \, s$Therefore,the time taken by the ball to reach the ground is:$t_2 = 5.25 - 0.25 = 5 \, s$Let $u$ be the initial speed of the ball at $t = 0$. For the motion of the ball:Displacement $s = -85 \, m$ (downward),Acceleration $a = -g = -10 \, m/s^2$,Time $t = 5 \, s$.Using the kinematic equation:$s = ut + \frac{1}{2}at^2$$-85 = u(5) + \frac{1}{2}(-10)(5)^2$$-85 = 5u - 125$$5u = 125 - 85$$5u = 40$$u = 8 \, m/s$

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