How Does a Coin Roll in a Circle Without Falling?

[Sam_Goldberg]

Hi guys, I have an extremely simple conceptual question. According to my textbook (in a problem), "if you start a coin rolling on a table with care, you can make it roll in a circle... the coin leans inward, with its axis tilted." I ask: how is this possible? The center of mass of the coin undergoes circular motion, yet the only forces that will ever be on the coin is the weight and normal force, which can never point in the centripetal direction. Thus, where am I going wrong?

 

[Sam_Goldberg]

Never mind, there has to be friction pointing inward. I got it.

 

[noamholz]

Allow me to continue the question.
Why does it go in circles, and not fall (by tilting) while the CM's trajectory is linear
and in the the original direction?

in other words, what's the mechanism that makes the coin change it's direction or turn once it started tilting?

thanks