# Non-uniform circular motion, [stunt Car inside a ring]

1. Oct 20, 2011

### Krishan93

1. The problem statement, all variables and given/known data
[PLAIN]http://img695.imageshack.us/img695/3864/unled1dxu.jpg [Broken]

2. Relevant equations

F=(mv^2)/r

3. The attempt at a solution
NetForce=0
N-W=0

===
A free body diagram of the car at the bottom would just incorporate a downwards W force and an upwards N force together equalling 0, wouldn't it?

Last edited by a moderator: May 5, 2017
2. Oct 20, 2011

### Staff: Mentor

Those are the correct forces, but why would they add to 0? The car is accelerating!

3. Oct 20, 2011

### Krishan93

Accelerating as in change of direction?
I would think that the bottom of the loop is the maximum speed of the car, past that half the car begins to decelerate, no?

4. Oct 20, 2011

### Staff: Mentor

Yes. It's executing circular motion, so what kind of acceleration must exist?
You are told that the speed is constant.

5. Oct 20, 2011

### Krishan93

I think I got it. Knowing constant velocity did help.
Given the top of the loop circumstances, the only forces acting upon the car are N and W, together they equal the centripetal force.
Keeping the same velocity at the bottom, the N and W act against each other, but the centripetal force still has to equal that of when it was at the top in order to maintain circular motion.
Apparently N takes on a greater value to compensate I guess and I get an answer of 20.1

How's my reasoning? Is this the same reasoning with planes flying in a circular loop as well?

6. Oct 20, 2011

### Staff: Mentor

Good!
Similar considerations apply to anything moving in a vertical circle. (Of course, the speed of the plane will not necessarily be constant.)