The acceleration due to gravity is  meters/sec/sec.

The initial velocity of object is zero.

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Acceleration of a object is rate of change in velocity .

Velocity is .

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Substitute  in .

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Substitute .

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Substitute  in .

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The position of a object at time  is .

Velocity of  a object is rate of change in position .

Position at time  is  .

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The initial height of object is  feet.

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Substitute  in .

Substitute .

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Substitute  in .

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The object reaches the ground after  sec.

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Substitute .

 m.

The stone fall  m.

The velocity of an object is .

Substitute .

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Negative velocity means the object is falling down.

The impact velocity is m/sec.

The stone fall  m.

The impact velocity is m/sec.