Question

As your vacation job, you are driving a concrete mixer (mass 3300 kg). While driving down a hill (angle α = 29° with the horizontal), suddenly, a cow steps out on the road. You hit on the brakes, and with each locked wheel leaving 24 meters of skid marks, you come to a stop 47 cm before hitting the oblivious cow. The farmer yells at you and claims you have been speeding. Only a quick calculation, based on the length of the skid marks, would convience him that you have been driving responsibly.

You happen to know that the coefficient of kinetic friction between your tires and the road is 1.03. Thus, what was your speed?