# Homework Help: A Joule Car

1. Nov 15, 2007

### soulkiller

Hey guys, I am involved in a competition where my objective is to build a Joule Car:
Can anyone please give me ideas of how I can use gravitational potential energy to build it?

Here are the actual directions:

http://www.mrmaloney.com/nssl/events/2007-2008/0708_3-dec-joule-car.pdf

Your help would be appreciated guys!
Thanks

-A physics nerd:D

2. Nov 15, 2007

### mgb_phys

Not really an advanced physics topic ( unless you are planning to add anti-matter to the soup can and use the resulting ion beam as thrust).

You don't have much energy 0.3 * 0.2 *9.8 = 0.6J
So you need to keep the friction low ( below 0.6J/4m = 0.15 N )
I would look at having large light discs as wheels turning failry slowly.

You could have the can drop at the start, with a string around it, over a pulley and wrapped around the axle so that the falling can spins the axle ( like a pull starter on a lawnmower engine) then free wheel to the end of the course.

You could have a system of pulleys / gears so that the can falling 0.2m pulls a string a much longer distance and the unwinding string keeps tunring the axle all the way to the end.

You can do something similair having the can as some sort of piston, and using the compression of air to drive the wheel.