# physics

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a 145g baseball is dropped from a tree 13.0m above the ground. with what is the velocity of the baseball at the ground after it falls 13.0m? B. If it actually hits the ground with a speed of 8.0o m/s, what is the average force of air resistance exerted on it?

• physics -

Use conservation of energy to calculate the velocity at the ground with no friction.

V = sqrt (2 g H) = 15.97 m/s

If there is a lower velocity of 8.0 m/s, which is about 1/2 of the frictionless value, than about 3/4 of the available potential energy has been lost to friction.

Friction energy loss = (3/4)*M g H = ?

For the average force, solve
(friction energy loss)= (average force) x (13.0 m)

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