1. The problem statement, all variables and given/known data When an automobile moves with constant velocity, the power developed is used to overcome the frictional forces exerted by the air and the road. If the engine develops 30 hp, what total frictional force acts on the car at 120 mph? 2. Relevant equations 1hp = 746W 1mile-1609m work=force*distance power= work/time 3. The attempt at a solution 30hp= 22380w 120mph= 53.6448m/s I'm really not sure where to go from there, you need to end up with force which is Newtons, dont you need a mass in kg to for that?