Object sliding down a slope

1. The problem statement, all variables and given/known data
An object slides down a slope of 30° to the horizontal with CONSTANT VELOCITY.
Find the force of friction and the energy lost on the way down.

2. Relevant equations
$$\mu m g \cos \theta$$
$$\mu m g \cos \theta – m g \sin \theta = 0$$
$$W = K_2 + U_2 – (K_1 + U_1)$$

3. The attempt at a solution
I tried the following:

$$\mu mg \cos30 = mg \sin30 = \mu = tan30 \cdot m = 3,3 \cdot m$$

So the ratio is $$3,3m$$? It doesn’t sound right…
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

http://ift.tt/1jmIfn2