# Car rounds a flat road-friction forces

1. Mar 24, 2009

### Dannystu

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

A car, mass m=2500kg, rounds a curve on a flat road at a speed v= 15 m/s. The radius of curvature of the curve is r= 60m. There is obviously (static) friction between the road and the car tires, or the car would not stay on the curve.

2. Relevant equations

a.) Compute the centripetal acceleration experienced by the car.

b.)Compute the centripetal force experienced by the car. What phenomenon is the cause of this centripetal force?

c.)Compute the force of (static) friction between the tires and the road.

d.) If the given speed of V=15 m/s is known to be the maximum speed for this curve for which a car will not skid, compute the coeffiecient of static friction between the tires and the road.

3. The attempt at a solution

Part a)

Centripetal acceleration= V^2/r

=3.75 m/s^2

b.) Centripetal force = M*(V^2/r)

=9375N

c.) I have no clue on how to do part C and D, I know the formula for Static friction is

Fs= Coefficient of static friction * normal force

I calculated the normal force to be 24,500N (mass times gravity) since there are no other forces acting on the vertical direction. Can someone give me a push in the right direction?

2. Mar 24, 2009

### Dr.D

Draw a FBD and apply Newton's second law.

3. Mar 24, 2009

### Dannystu

Is the normal force equal and oppositely directed to the weight? I drew the FBD showing the a front view of the car.

4. Mar 24, 2009

### Dr.D

Write Newton's law in the vertical direction and find out.

5. Mar 24, 2009

### Dannystu

Yes because the car is not moving on the vertical direction, and the friction force in pointed in the opposite direction of motion.

Last edited: Mar 24, 2009