# Homework Help: Racecar and Centripetal Force

1. Oct 24, 2007

### Ryo124

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

A race car travels at a constant speed on a circular track. The net force on the car is 1600N. What kind of force creates the acceleration?

a) air resistance
b) friction tangent to the circle
c) friction toward the center of the circle
d) friction away from the center of the circle
e) force of the engine

2. Relevant equations

Concepts of centripetal acceleration and force.

3. The attempt at a solution

I know that it is not a; however, I am not sure what way the friction is directed or if the answer is e.

My main guess would be toward the center of the circle, since that is the direction of the acceleration, but I'm not sure.

Last edited: Oct 24, 2007
2. Oct 24, 2007

### Math Jeans

You are correct, the answer is not a. It is also not e because the car is traveling at a constant speed. It is not d because if the friction was away from the circle, then it would mean that the centripedal force would be inward, which is not the case. The friction tangent to the circle is not the case either because the car is traveling at a constant speed meaning that the engine is overcoming that force.

You are correct, the answer is the frictional force towards the center as without it, the car would just fly off in a straight line tangent to the track.

I hope I helped.

3. Oct 24, 2007

### Ryo124

You did help, but isn't the centripetal force directed inward, toward the center of the circle?

What would happen if friction was away from the circle? Would the car just fly off the track?

4. Oct 24, 2007

### Math Jeans

Oh. sorry. I got that mixed up. It is inward, I meant the force pushing the car outward.

The friction CANT be away from the circle. If the friction pointed outward, then there would be a force trying to pull the car into the circle, not outward. Friction can only counteract forces, it cannot add to them. For the friction to be in the same direction as the force pushing the car outward is impossible, however, yes the car would fly off the track.