**1. The problem statement, all variables and given/known data**
A coin(radius=r) rolls in a funnel only with a horizontal speed v. The coin always stays at his altitude.

The coin has a homogen mass distribution and it only rolls! So it has a translational motion and a rotation motion.

Find a function R(z) whitch discribes the form of the funnel!

R>>r and z is the altitude of the funnel. the z-coordinate of the coin is changeless.

**2. Relevant equations**
I thougth it must be [tex] \tan\alpha=\frac{v^2}{r\cdot g}[/tex]

But then i tought the speed at all parts of the coin isnt the same.

If there are any questions in understand my problem, ask!

I made a drawing of that:

Can u pls help me?

Thank you

**1. The problem statement, all variables and given/known data**
**2. Relevant equations**
**3. The attempt at a solution**