Elastic Potential Energy stored in rubber band

1. Oct 7, 2007

Phykid

Hello Everyone.

It has a year since I have worked with Elastic Potential Energy & I have forgotten the formula to work it out.
I have this question and would appreciate it if anyone could tell me how to do it, or tell me the formula of how to work it out.

So here it is:

Rachel pulls back a 0.002 kg rubber band and flicks it across a room with a speed of 10m/s.
What was the elastic potential energy stored in the rubber band just before it was released?

Thanks,
Phykid

2. Oct 7, 2007

Hootenanny

Staff Emeritus
3. Oct 7, 2007

Phykid

Thanks for the very fast reply, but that is a little to complex for me!
I just need to know how to find the EPE using the mass & speed.

Thanks again,
Phykid

4. Oct 7, 2007

Hootenanny

Staff Emeritus
Yes you do, but can you work out the kinetic energy...?

5. Oct 7, 2007

Phykid

Yes, 0.1J if I have done it right.

(Please excuse the newbie questions. I'm only 14 and not done this in a year)

6. Oct 7, 2007

Hootenanny

Staff Emeritus
Spot on, so where do you think that the elastic band got this kinetic energy from?

7. Oct 7, 2007

Phykid

The stretch? :)

8. Oct 7, 2007

Hootenanny

Staff Emeritus
Correct, so how much potential energy was stored in the band?

9. Oct 7, 2007

Phykid

0.1? :s
You've just lost me

10. Oct 7, 2007

Hootenanny

Staff Emeritus
Correct!

When you let go of the elastic band, it flew off somewhere with 0.1J of kinetic energy. That kinetic energy couldn't have just 'appeared' from somewhere; the energy was stored as potential energy in the elastic band as you were stretching it. When you let go of the elastic band, this potential energy was turned into kinetic.

Does that make sense?

11. Oct 7, 2007

Phykid

Brilliant :D

Thanks alot, for your help & patience :)

12. Oct 7, 2007

Hootenanny

Staff Emeritus
No problem