Question

After falling from rest at a height of 29.2 m, a 0.488 kg ball rebounds upward, reaching a height of 20.3 m. If the contact between ball and ground lasted 1.68 ms, what average force was exerted on the ball?

I'm so confused on where to start. tyvm

Answer 1

Calculate the momentum change due to the bounce.

Then use the relation:
Impulse = (avg. force)*(time) = momentum change

Answer 2

What do you mean by momentum? F=ma? thanks so much sorry to bother you

Answer 3

So glad someone is confused as I am! There are a lot of things on here that will not give you the write answer, but this will come pretty darn close!

There are four main calculations you need to make:

1) Find Velocity after falling (V1)
2) Find velocity on the way up again (V2)
3) Find the momentum change
4) Since (avg force)*(time)=momentum change, divide the change in momentum (found in #3) by the time to get average force.

DO NOT FORGET TO CHANGE YOUR TIME INTO SECONDS (divide ms by 1000).

For 1 & 2, use kinematic equation:
squarert: (2*9.8*Height) [9.8=gravitational acceleration]

For 3, use: m*(V1=V2)

For 4, use: momentum change/time in seconds

Hope this helps someone in the future!