# Need help- Force of friction in a circle.

1. Nov 3, 2009

### Socom

1. The problem statement, all variables and given/known data
A 45-kg merry-go-round worker stands on the ride's platform 6.3m from the center. If her speed as she goes around the circle is 4.1 m/s, what is the force of friction necessary to keep her from falling off the platform?

2. Relevant equations
f=ma
Ac=v^2/r
mu=v^2/rg (derived from [mu]g=v^2/r

3. The attempt at a solution
I don't believe the 6.3m is relevent to the problem.

I believe Fnet=sigmaFx=theta=m*a

I am not really sure how to attack this problem and some help would be very nice.

2. Nov 3, 2009

### Pythagorean

You got the right equation:

$$\mu = \frac{v^2}{rg}$$

now tell me... what does the r mean in:

$$A_c = \frac{v^2}{r}$$