# Homework Help: Circular Motion of a car on a curve

1. Oct 19, 2006

### FossilFew

If a curve with a radius 88m is perfectly banked for a car traveling 75 km/h what must be the coefficient of static friction for a car not to skid when traveling at 95 km/h?

95km/h = 26.4m/s
75km/h = 20.8 m/s

v^2/gr=Us
Us= (95^2/(9.81* 88) = 10.5 ( This seems too large)

2. Oct 19, 2006

### Hootenanny

Staff Emeritus
How are you taking into account the banking of the curve? Don't forget that a component of the normal force will provide some of the required centripetal force. What do you think "perfectly banked" means?

3. Oct 19, 2006

### FossilFew

We just got into circular motion so being a circular motion newbie I can only give you a newbie answer. My interpretation of perfectly banked means there is a force pushing the car towards the center of the track. I'm not sure how to use that explanation (assuming it is correct) into an equation.

Thanks!

4. Oct 19, 2006

### OlderDan

Perfectly banked means that the driver of the vehicle does not feel like s/he is being pushed sideways relative to the seat. Equivalently, it means there is no force making the tires slide up or down the track. What does this tell you about the force of friction when the car is travelling at the "perfect bank" speed of 75 km/h?