Final answer:
The force of friction depends on the normal force and the coefficient of friction, where the normal force is exerted by the surface and the coefficient represents material resistance.
Step-by-step explanation:
The two factors that affect the force of friction are 1) the normal force and 2) the coefficient of friction. The normal force is the perpendicular force exerted by a surface onto an object, which is equal to the weight of the object when it is on a horizontal plane. The coefficient of friction is a unitless value that represents the amount of frictional resistance between two surfaces in contact and depends on the material properties of the surfaces.
The formula for the static friction force is fs \u2264 Ms \u00d7 N, where Ms is the coefficient of static friction and N is the normal force. Similarly, the kinetic friction force is represented by = Mk \u00d7 N, where Mk is the coefficient of kinetic friction. It's important to note that the normal force can be less than the object's weight if it is on an inclined plane.