# A 0.25kg ball is dropped from a height of 5m. It bounces back to a height of 4.05m. If the impact of the

ball with floor lasted 0.01s, find the average force that the floor exerted on the ball.

Steps:

•

Find the velocity of the ball immediately before it hits the ground (use kinematics: therefore you need

a picture, define your coordinate system etc).

•

Find the velocity of the ball immediately after it hits the ground (kinematics again) (use the same

coordinate system that you defined for the way down).

•

BONUS draw position, velocity and acceleration versus times graphs for the bouncing ball.

•

Then use the definition of

a

av

=

v

t

to find the average acceleration.

•

Draw a FBD of the ball hitting the floor including the direction of the acceleration. Apply Newton's

second law in the vertical direction and solve for the normal force

ec facilisis. Pell**acinia pulvi**