Average force on a 0.47 kg ball bouncing from 34 m to 24 m

[bunton33]

Homework Statement

After falling from rest from a height of 34 m, a 0.47 kg ball rebounds upward, reaching a height of 24 m. If the contact between ball and ground lasted 1.8 ms, what average force was exerted on the ball?

Homework Equations

vf^2=2gh

vf=sqrt 2gh.

force*time=2sqrt(2gh)

The Attempt at a Solution

i have tried to plug in but i cannot seem to get it correct. help please!

 

[Delphi51]

Look up the concept of "impulse" in your textbook or Wikipedia. The impulse formula will make short work of this problem!