 I've always hated the word normal force because I don't think that describes what's actually going on with this force. If I had my way, we'd always call it the right angle force because in all the different situations we look at in physics 20, this force is always acting at a right angle to the surface. The normal force occurs whenever an object is resting against a surface, and there's sort of three different situations we look at here in physics 20. The first situation is when an object is on a horizontal surface and it doesn't have any vertical acceleration. In these situations, the normal force is at a right angle to the surface and it points straight upwards, and it's going to be exactly equal in magnitude but in opposite direction to the force of gravity. The second situation is if there is vertical acceleration, and we see situations like that when you've got a roller coaster or a loop-the-loop or maybe you've got an elevator that's accelerating upwards or downwards. So in these cases, there is a net force and we'll find the normal force by doing a net force statement. The third situation is if the object is on an inclined plane. Here if we draw a free body diagram of the forces acting on the object, we can see that the force of gravity kind of breaks into two components. One of them is the parallel force of gravity down the ramp, and the other one is equal to the normal force. The normal force is still at a right angle to the surface, but now we're going to calculate it by multiplying the cosine of theta by the force of gravity.