(adsbygoogle = window.adsbygoogle || []).push({}); 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!

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# Homework Help: Gravitational and kinetic energy problem

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