Sample problem

A 2.0 kg block is placed on a 30 degree inclined plane. The block is connected to a mass m by a string that passes over a pulley at the top of the incline. Mass m hangs vertically from the string. The coefficients of friction for the block and the plane are: ms = 0.4 and mk = 0.3.

If m is 0.2 kg and the system is released from rest, what is the acceleration?

The place to start, as usual, is with the free-body diagrams of the block and the mass. This is a little problematic because we don't know whether the system is accelerating, so it's not immediately clear how to handle the force of friction.