Problem

A ball is dropped off the top of a 56 m tall tower. The ball is initially at rest. Calculate the time it takes to reach the ground. Calculate the impact speed. Neglect air resistance.

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Solution

The acceleration due to gravity near the surface of the Earth is . The initial velocity is .

To solve for the time, use the formula . For this problem . Since the height of the tower is 56 m tall, the initial position is 56 m and the final height is 0 m.

.

Therefore,

.

The impact velocity can be calculated in two ways.

Method 1

Thus, the impact speed is 33.12 m/s.

Method 2

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