Homework Help: Accelarating on a curve please help soon

1. The problem statement, all variables and given/known data
A flat (unbanked) curve on a highway has a radius of 260 m. A car rounds the curve at a speed of 18.0 m/s . What is the minimum coefficient of friction that will prevent sliding?


2. Relevant equations

A= v2/R I got the acceleration but the problem does not give the mass for caluculating the normal force

3. The attempt at a solution
1.246 m/s is what I got for the acceleration after that I do not know what I should be doing.

 

the centripital force is v2/R but I can not think of what i need to equate it to Fnet= Fn-fk=ma but I do not have mass or I might be totally spacing something I should know but I am looking through my notes and can not find or think of anything