# Banked curve with friction, but no angle

1. Oct 23, 2013

### puzzledup

1. The problem statement, all variables and given/known data
A banked curve has been designed so that it is safest for a vehicle going 70 mph. The topography of the land restricts the radius of the road to 300m. Assume mu(static friction) is 0.80 and mu(kinetic friction) is 0.60.
A 5512 lb vehicle travels with a speed of 60 mph on the curve.
1. Calculate the force that the road exerts on the vehicle.
2. Calculate the friction on the tires.

2. Relevant equations
F=ma
Centripetal acceleration=v^2/r

3. The attempt at a solution

converted all mph's given to m/s and converted weight in lbs to N.
tried to find the angle by:

v^2/r=Wsinθ

I came up with 19.45 degrees. This just doesn't seem right, that's an awfully steep bank.

2. Oct 23, 2013

### Staff: Mentor

How did you arrive at this? Note that the units do not match: The left side is an acceleration, while the right is a force.

3. Oct 30, 2013

### puzzledup

I was wrong in that angle. I found the correct angle by assuming no friction, solving the y force for Fn and substituting it in the x force equation. This gave me theta.
Then, after figuring out the x y axis could be rotated to go with the Fn on the car, solved like any other incline plane problem.