Box sliding on incline with friction

[Stuck/:]

Homework Statement

How to find the uk of a box sliding down a hill with only an angle and acceleration

Given: angle= 30 acceleration= 3.1 m/s2

Homework Equations

1. uk= fk/fn 2. f=ma

The Attempt at a Solution

i did the cosine of my angle but i am not sure that is the answer

 

[pgardn]

Homework Statement

How to find the uk of a box sliding down a hill with only an angle and acceleration

Given: angle= 30 acceleration= 3.1 m/s2

Homework Equations

1. uk= fk/fn 2. f=ma

The Attempt at a Solution

i did the cosine of my angle but i am not sure that is the answer

Have you done free body diagrams where you "break" the force due to gravity up into two components? One of the components is opposite the normal force, and the other is directed down and parallel to the hill...?