Kinetic Friction on inclined plane problem

[VinnyCee]

Been trying to comprehend this one for a few hours:

The coefficient of kinetic friction between a block and an inclined plane is 0.20 and the angle is 60 degrees.

What is magnitude of a? The book says 7.5 m / s^2
How do I figure this with no speeds or distances or even a mass?

 

[doxigywlz]

you got to do your free body diagrams! those stupid things... remember? the sum of all forces = ma unless the velocity is constant. do one for the x side and one for the y side, incorporate your co. of kinetic friction and the angle (probably cos60 and sin60 from mg)... help any? i have a lot of trouble with these, too

 

[Pyrrhus]

Like doxi said use a freebody diagram then

Apply Newton's 2nd Law

$$\sum_{i=1}^{n} \vec{F}_{i} = m \vec{a}$$