What is the Relationship Between Energy and Friction on an Inclined Plane?

[slaw155]

Homework Statement

EDIT: I have solved it entirely myself.

Homework Equations

The Attempt at a Solution

 

[haruspex]

Homework Statement

A 750kg mass car with initial speed 110km/h coasts up a slope inclined at 2.5degrees to the horizontal to a height of 22m above its starting point. What is the average force of friction?

Homework Equations

No real clue about this one

The Attempt at a Solution

As above, I don't really have an idea on how to do this. I've drawn a force vector diagram and considered energy but can't seem to work it out.

Even so, you are required to post your attempt, so far as it goes.

 

[slaw155]

Even so, you are required to post your attempt, so far as it goes.

I have worked it out entirely using my own self-determined methods.

 

[dean barry]

Without friction the initial KE should equal the final PE.

 

[HallsofIvy]

With friction, final PE should equal initial KE minus energy lost to friction- the friction force times the distance traveled.

 

[dean barry]

So :

The initial KE - the final PE = the energy lost to friction
= ( ½ * m * v ² ) - ( m * g * h )
( Joules )

Over the length of the incline, the energy lost to friction = ( constant ) friction force * distance travelled
( the length of the incline = 22.0 / ( sine 2.5 ° ) )

So, then, the friction force must equal ( ( initial KE ) - ( final PE ) ) / distance travelled

Comments please.