NO I meant change in KE on a flat surface where distance is given.?

Question

It's okay I solved it though, that answer was comprehensive, thanks.

Answer 1

What I said about inclined surfaces works just the same on a horizontal surface; you will compute sin(theta)=0 and cos(theta)=1 so the normal gravity force=g*m and there is no gravity force parallel to the surface.
When KE or PE decreases due to friction energy loss, the decrease equals the friction energy loss which is friction force * distance. I assumed you already knew that. If my answer helped I'm happy. I'd appreciate it if you go back to that question and select my answer as best; this is the normal procedure even though it would eventually be selected by public vote.
P.S. A tip on yahoo answers. I only found this question by accident. You can add followup questions to your original question; just click on the original question and there should be a link that lets you add more words, probably called Additional Details. That's what I was referring to when I said I'd be checking for followup questions.