Block on a Frictionless Plane
This Mathematica Demonstration of a block on an inclined plane which shows the forces acting on the block depending on the angle of incline.
It includes the ideas of both normal contact forces and friction (which is why we reference it from both sections!)
As an exercise, you might consider resolving forces acting on the block to obtain an expression for the net force acting down the slope at some particular angle.
(Tip! The first thing to do here if you are trying to do this is to draw a good (and large) diagram! You will need to identify the two similar angles that characterise the slope and therefore appear in your various components of forces..... the worked example in S2.8 will help!)