Maximum safe speed on a circular racetrack with friction

[saikamaniac]

Friction provides the centripetal force necessary for a car to reval around a circular flat racetrack. What ios the maximum speed at which a car can travel safely around a track of radius 80m if the coefficient of friction between the tyres and road is 0.3?

I really have no idea how to attempt this question...

 

[HallsofIvy]

Do you know how to calculate the "centrifugal force" on the car? The friction force, equal to 0.3 times the weight of the car, must be equal to that.

 

[saikamaniac]

well the centrifugal force is just equal but opposite to the centripetal force
which i don't know...and i don't know the MASS of the car and thus can't calculate the weight

 

[GoldPheonix]

A common thing for people who are just starting physics is to forget that, often times, mass is irrelevant to finding a solution.

The centrifugal forces must equal friction, correct? What do you do when two equations equal each other?

Whenever I get stuck, I like to just starting writing off my known equations:

$$\Sigma F_c = m\frac{v^2_t}{r}$$

$$F_f = \mu m g$$