# Homework Help: Help on inelastic problem

1. Mar 31, 2004

### psruler

Hi!

How do i find change in kinetic energy?

Here is the problem:
The rubber ball is dropped 2m elastically off the floor, so its speed immediately after bouncing is the same as immediately b4.
If the rubber ball has a mass of 0.015kg and its velocity is 6.26m/s, what is its change in kinetic energy from immediately b4 the collision to immediately after the collision? Breifly justify your answer.

Do i use this equation, KE = 1/2mv^2?

THANKS!!

2. Mar 31, 2004

Yup. Change in kinetic energy is just the kinetic energy after minus the kinetic energy before.

So KE = 1/2*mv^2, now if m is the same for both and v is the same for both...

3. Mar 31, 2004

### psruler

4. Mar 31, 2004

Hold on now!

1/2(.015kg)(6.26m/s)^2 - 1/2(.015)(6.26m/s)^2 = ?

Also, what units do you get? Here's a hint: it's not Newtons! It's kinetic energy, so its units will probably be energy.

5. Mar 31, 2004

### psruler

I got 0 joules.

6. Mar 31, 2004