What is the minimum radius of curvature of the curve?

[gap0063]

Homework Statement

A civil engineer is asked to design a curved
section of roadway that meets the following
conditions:
With ice on the road, when the coefficient of
static friction between the road and rubber is
0.1, a car at rest must not slide into the ditch
and a car traveling less than 80 km/h must
not skid to the outside of the curve. The road is banked at an angle of 5.71059 degrees
What is the minimum radius of curvature of
the curve?

Homework Equations

I thought the equation to use was v^2= gr tan (theta)

The Attempt at a Solution

the equation is used above gave me a wrong answer

 

[Vyse007]

If you use that equation, you won't be taking into account the effect of friction. Since the coefficient of friction is provided to you, you can use it in the equation u=v^2rg, where u is the coefficient. That might work for the case when the car is moving at 80km/hr(take care of the units...if r is in m, then convert v into m/s. I know its silly but it happens a lot).