A ball is released from rest at a height of 15 metres above ground level. Find the speed of the ball when it hits the ground, assuming that no airresistance acts on the ball.

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justaguide eNotes educator| Certified Educator

The ball is released from a height of 15 m above ground level. It moves down due to the gravitational force of attraction of the Earth and the acceleration is 9.8 /s^2 in a vertically downwards direction.

If an object starting with an initial velocity u and a final velocity v travels a distance s at an acceleration a, v^2 - u^2 = 2*a*s

In the problem u = 0, v has to be determined, a = 9.8 and s = 15 m, substituting the values in v^2 - u^2 = 2*a*s

=> v^2 - 0 = 2*15*9.8

=> v^2 = 294

=> v = `sqrt 294`

=> v = 17.146 m/s

The speed of a ball that is dropped from a height of 15 m when it hits the ground is 17.146 m/s

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