Normal and Friction Forces
The applet at right illustrates the dependence of the normal and frictional components of a contact force upon other forces. When you click on "Go", the applet displays a representation of a box with gravitational force (W), a pull (P), and the normal (N) and frictional (f) contact force components. The box is assumed to be moving to the right, so that kinetic friction is to the left, and there is no acceleration in the vertical direction.