# Power and velocity

1. Nov 20, 2012

### Darth Frodo

1. The problem statement, all variables and given/known data
(a) A car of mass 1365kg has 60kW engine and a max speed of 145km/hr. Find the frictional resistance.

(b) Calculate max speed of car up a gradient of 1 in 5 if Friction stays the same.

2. Relevant equations

P = F.v

3. The attempt at a solution

60000 = F (40.2m/s)
F = 149205 N

(b) P = netF . V
60000 = (1492.5 + mgsinθ)
θ = angle of inclination
60000 = [1492.5 + (1365)(9.8)(1/$\sqrt{26}$)]V
v = 60000/4118.6 = 14056 m/s

Is this correct?

2. Nov 20, 2012

### Delphi51

It looks good to me!

The question isn't quite right; friction will not remain the same as the speed changes.