Physics Homework

Alright guys, I've been working on this problem for hours.  We're going over rotational motion, but I just can't understand it.

A car traveling on a flat(unbanked) circular track accelerates uniformly from rest with tangential acceleration of 1.70 m/s^2.  The car makes it one fourth of the way around the circle before it skids off the track.  Determine the coefficient of static friction between the car and the track from this data.

I've tried what seems like a million ways to solve this, but I keep getting wither radius or velocity left over.  Any chance you could help?

.572

but how?

It just is.

Fc = Ff (Centriptal force equals force of friction)
Fc = m*v*v/R (Centripal force is mv^2 / R)
Ff = k*m*g  (Frictional force is Normal force times coefficient of friction)

v*v/R = k*g (Set the two equations equal - mass cancels)

D = .5*a*t*t (Distance is 1/2 a t^2)
pi/2 * R = .5*1.7*t*t (It travels a quarter circle, or pi/2 times the radius)
t = sqrt(pi*R/1.7) (Solve for t - the time it takes to go a quarter circle)

v = a*t (velocity is acceleration times time)
v = 1.7*sqrt(pi*R/1.7) (This is the velocity when the car slides off the track)

v*v = k*g*R (Back to the original equation now that we know v)
1.7*pi*R = k*g*R (The R is gunna cancel)

k = 1.7*pi/g (Or .544)

do you have centrifugal acceleration as a function of tangential velocity? seems like just balancing forces