Here is the problem: When the jet-powered car "Spirit of America" went out of control during a test drive at Bonnevile Salt Flats, Utah, it left skid marks about 18.70km long. If the car was moving initially at a speed of 661.0km/hr, estimate the coefficient of kinetic friction between the tires and the road. I know that the coefficient of kinetic friction can be found using the equation: fk = u * N where u is the coefficient and N the normal force. But I cannot understand how I am supposed to find it with only the speed and distance. I tried finding the time (assuming V=0) then finding the acceleration and them finding the force with F=ma. But I was unsure if the f in the f=ma equation was equal to the f in the f=uN equation. P.S.(I have converted the distance to meters (18700) and speed to m/s (186.618)) Thanks for your help and time!