When a ball is thrown down from the top of a building 75 m high it takes 3 seconds to reach the ground. If thrown upwards at the same speed how high will it go.

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When the ball is thrown downwards it accelerates downwards due to the gravitational force of attraction of the Earth at 9.8 m/s^2. If an object has an initial velocity of u m/s and it is accelerating at a m/s^2, the distance traveled by the object in time t is given by D = u*t + (1/2)*a*t^2

Substituting the values given in the question,

75 = u*3 + (1/2)*9.8*9

=> u = 25 - 14.7

=> u = 10.3 m/s

If the ball is thrown upwards at 10.3 m/s, the height to which it rises is equal to h where (1/2)*(10.3)^2 = 9.8*h

=> h = 5.41

The ball rises to a height of 5.41 m

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