physics
posted by Sasha .
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?

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)