What Is the Safest Speed for a Banked Curve with Ice?

[Jtappan]

Homework Statement

A curve in a highway has radius of curvature 120 m and is banked at 3.5°. On a day when the road is icy, what is the safest speed to go around the curve?
_________ m/s

Homework Equations

m(v^2/r)?

The Attempt at a Solution

How are you suppose to find this if you don't know the static friction coefficient?

 

[Astronuc]

I think the point is that the road is icy, so no friction. The road is bank so the weight of the car is at an angle with the normal to the road.

See this - http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/carbank.html - and determine the case when there is no friction.