It is good practice in physics to draw a diagram of the situation, so the first thing we want to do is create a picture of the problem, focussing on the object on the slide. Now we need to analyse what is happening in the problem. Is the mass sliding down? Is it attached to a rope and the rope connected to another mass hanging down from a pulley? Do we consider friction or not? Once we have established this, we can draw a free body diagram for the mass analysed and show all the forces acting on it, understanding the components of each force. Now the only thing we need to do is apply Newton's second law in the direction of motion and solve for the variable we're looking for.