How to find Friction Force and Coefficient of Friction?

softball1394

1. The problem statement, all variables and given/known data

A horizontal force of 200 n is required to cause a 15 kg block to slide up a 20degree incline with acceleration of 25 cm/s^2. Find the friction force on the block and the coefficient of friction.
Friction force = 134N
Coefficient of Friction = 0.65

2. Relevant equations
Ff = u Fn

3. The attempt at a solution
I can't figure out where to begin.
I'm not sure if it's relevant, but I found:
Fg to be 147.15 N
horizontal component to be 50.33 N
Vertical component to be 138.28N

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softball1394

anyone there?

Part one:
Fgcos(20) - Ff = ma
138.28N - Ff = 15 x .25m/s^2
138.28N - Ff = 3.75
-138.28 -138.28
-Ff=-134.53
Ff=134.53N
(Hopefully this is correct?)

Part 2:
Ff = u Fn
u = Ff / Fn
u = 134.53N / 138.28N
u = .97

But the answer should be .65.
What am I doing wrong? The normal force should be 138.28 because 147.15cos(20) is 138.28, right?

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