1. The problem statement, all variables and given/known data Given: 1 hp = 746 W and 1 m/s =2.237 mi/h. When an automobile moves with constant velocity, the power developed in a certain en- gine is 85.4 hp. What total frictional force acts on the car at v = 72.8 mi/h? Answer in units of N. 2. Relevant equations Kinetic Energy=.5mv^2 Disspated energy=F*displacement <-the f would be the frictional force. W=change in energy(J)/change in time(s) 3. The attempt at a solution i first converted 85.4 hp to W: 63708.4W then the v to m/s: 32.54m/s i would like to find the amount of joules in 63708.4W, but I dont know the time. So I probably need to find a way to cancel it. also, I don't know the mass of the car...nor the displacement. I'm not sure of what to do with so many unknowns. Can someone point my problems out? Ty in advance!