# Spinning wheel problem

1. Aug 3, 2004

### zarcon

Hi All! This is my first real post here.

I have a pretty basic question regarding rotating objects and the manner in which the rotation becomes a translation.

If I drop a bicycle wheel against the ground, it bounces back toward my hand. But if the wheel is spinning as it falls, it will move forward after it bounces.

I know (think) this is because of the opposing friction from the contact of the spinning wheel and the ground, but a diagram of the forces would show a frictional force perpendicular to the wheel's center of mass. Shouldn't this then be a completely rotational force?

If the wheel is floating perfectly still in space and a force is applied perpendicular to the wheel's center of mass, it will cause the object to spin without any linear translation, like a basketball on the end of somebody's finger, or a plate on a stick, right?

So a perpendicular force applied opposite to the direction an object is rotating will cause it to move in the direction of the force? Is that right? How would that be calculated?

Thanks! Hope I made my question understandable. Anything to point me in the right direction would be really appreciated.

Jonathan

2. Aug 3, 2004