Practice!

Sample Problem

A block rests on an inclined plane. What are the forces on acting on this block?

Solution

Because force (a) is exerted perpendicular to the surface the block rests on, it is the normal force. Because force (b) is exerted against the direction of the possible motion, it is frictional. Because force (c) is exerted straight down, it is the force of the weight of the block.