"A child rides a wagon down a street with an inclination angle of 38.0 degrees. In order to keep from moving to fast, the child has secured the wheels of the wagon so that they do not turn. The wagon and the child then slide down the hill at constant velocity. What is the coefficient of kinetic friction between the tires of the wagon and the pavement?" I've thought about this for awhile. I had thought that the coefficient of kinetic friction would equal the coefficient of static friction (because the net force at constant velocity and at rest equals 0), but now I'm not sure. I'm fairly certain that the coefficient of kinetic friction can't equal 0 (there would be no friction at all then), but beyond that I'm not sure. Any ideas?