Circular motion with no frictional force

[lucas1]

I need a formula for an angle with which there is no frictional force during circular motion. No data. No hint.

My teacher gave us such task on the latest test. She said that it is easy we just need to think. Nobody solved it. I don't know now if we are such fools or she is a poor teacher that gives exercises on tests without prior solving similar ones. To improve YOUR mood: she teaches on IB Diploma and she hasn't said anything this year in English and she spelled frictional force on test: "ficktional". Also we do mainly theory on lessons while tests are only tough exercises. Nevertheless any ideas? Is it commonly used formula? Can You show how to get to it?

 

[technician]

Your teacher is not silly!
She has asked a very perceptive question.
I think that she is asking about 'banked' tracks where car, bob sleighs etc can follow a curved path without relying on friction.
I think she wants you to look at vertical and horizontal forces on a banked track and show that it is not necessary to have friction!
Hope this helps...if you still have problems come back