1. Feb 23, 2008

### A_lilah

1. The problem statement, all variables and given/known data

What is the smallest radius of an unbanked (flat) track around which a bicyclist can travel if her speed is 29 km/h and the coefficient of static friction between tires and track is 0.29?

2. Relevant equations

coefficient of static friction = (f of maximum static friction / Normal force)

fnet = ma = m * v^2 / r

3. The attempt at a solution

If an object is moving, isn't their just kinetic friction? I get that the normal force is the acceleration, but how can there possibly be a maximum static friction at this point?

Here's what I've got:

29km/h = 8.0556 m/s

.29 = fstatmax / a, therefore a = fstatmax / .29

Fnet = m* a = m * (v^2 / r)
Fnet = a = v^2 / r
fstatmax / .29 = (8.0556)^2 / r

Thanks for any help!

2. Feb 23, 2008

In case of tyres, the bottom-most point is instantaneously at rest. That's why static friction.

f=0.29Xmg.
$$f=\frac{m{v^2}}{r}$$

solve to get r.

3. Feb 23, 2008

### A_lilah

Ah...
thank you for the help!