# Bead and loop-the-loop: normal force?

1. May 1, 2007

### Physicist

1. The problem statement, all variables and given/known data

A bead sliding around a loop the loop. Given its mass and speed at the top of the loop, we want the normal force on it.

2. Relevant equations

mv^2/r = mg + N

3. The attempt at a solution

I have the correct solution that the normal will be downward. My question is from what would this normal force exist? I mean if the bead has a hole that the track is passing through, how can we understand normal force (that comes from the contact between the bead and the track).??

Thank you

2. May 1, 2007

### PhanthomJay

Say the hole in the bead was oversized, you know, the track might be 1 cm diameter wire, but the hole in the bead is 2cm. Do you think that the bead stays in contact with the track at the edge of the hole interface, or does it pass through it without the edges of the hole touching the rail?

Last edited: May 1, 2007
3. May 1, 2007

### Physicist

Maybe if it is moving with a hight speed it not touch the rail.

Do you mean that the normal force here is a result of circular motionand is different from the normal exerted by, say, a table on a book that placed on it??

4. May 1, 2007

### PhanthomJay

Yes, the normal force is necessary in order to keep the bead moving in a circle. But you're wrong about the bead not touching at high speed, the greater the speed, the greater the normal force, so there must be contact.

5. May 1, 2007

got it..

Thanks