Centripetal acceleration

[caccers]

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

I am having difficulty with a problem: A race care goes around a level, circular track with a diameter of 1.00 km at a constant speed of 90.0 km/h. Wha tis the car<s centripetal acceleration in m/s^2?

2. Relevant equations

Ac=v^2/r

3. The attempt at a solution

I'm not quite sure if I'm supposed to find the radius of the 1.00 diameter or if I simply use the 1.00 km as my radius in the above equation...?

[rock.freak667]

..a=\frac{v^2}{r}

r=radius...so yes you must find the radius(which is half of the diameter!).

[Kurdt]

Radius is half the diameter.