1. The problem statement, all variables and given/known data Hi, (firsly apologies for posting in wrong area originally) I'm new to the forum and this is my first post....so go easy!! I have a physics problem to solve and if possible I would love a bit of help here. This is the question: A standard car is driven around in a measured circle, increasing its speed as it goes and is able to reach 85mph before it loses traction and slides away. A racing car, with spoilers and wings fitted, produces twice the amount of downforce as the standard car. It is driven around the same circle and in the same circumstances. How fast can the racing car drive around the circle until it too breaks away and loses traction. The formula given to calculate the answer is: v =[Square root of] u g r (where v = final velocity, u = co-efficient of grip and is a constant, g = gravity, and r = radius of circle.) Given that gravity would normally be a constant at land level (I believe) and the coefficient of grip is a constant, I am struggling to understand how the doubled downforce would fit into this equation. Hence, how would I calculate the critical speed of the racing car? Any help here would be much appreciated. 2. Relevant equations v =[Square root of] u g r (where v = final velocity, u = co-efficient of grip and is a constant, g = gravity, and r = radius of circle.) 3. The attempt at a solution I am happy with gaining a value for the radius from the standard car and this will also then be used for the racing car, but I am struggling with what the down force effect will do. I researched other similar questions and generally there would be a mass involved to assist in calculating the change of the down force, but there was no mass given in this example and so the friction coeffiecient is what I would expect to see as the factor which would be doubled. However, the question did state that the friction co-effiecient was constant (which I understand to mean it will be the same for both vehicles), so this has thrown me. Any pointers on how I am going wrong here would really help!!