# Car banked problem

1. Oct 11, 2005

### confusedaboutphysics

A 1300 kg car rounds a curve of radius 70 m banked at an angle of 12°. If the car is traveling at 88 km/h, how much friction force is required?

ok so this is what i did so far but i got stuck.

the sum of Fy = mg - Fncos(angle) + Ffrsin(angle) = ma = 0
the sum of Fx = Fnsin(angle) + Ffrcos(angle) = ma = mv^2/r

i dont know how to get Ffr alone from here...help please!

2. Oct 11, 2005

### Tom Mattson

Staff Emeritus
In your math courses this would have been called a system of equations. Your system here is 2 by 2 (2 equations, 2 unknowns). You can solve it by substitution. That is, solve for one of the variables in one of the equations, and then substitute the result into the second equation to eliminate one variable.

3. Oct 11, 2005

### confusedaboutphysics

so are my two unknowns Ffr and a?

4. Oct 11, 2005

### Tom Mattson

Staff Emeritus
No, they are the frictional force and the normal force. You do know a.

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