In general, how is the frictional force related to the normal force?

The frictional force is directly proportional to the normal force, which is a key principle in classical physics. This relationship can be understood through the equation that defines the frictional force: ( F_f = \mu F_n ), where ( F_f ) is the frictional force, ( \mu ) is the coefficient of friction (which depends on the materials in contact), and ( F_n ) is the normal force acting on the object.

The normal force is the perpendicular force that a surface exerts on an object resting on it. As the normal force increases (for example, if more weight is added to the object), the frictional force also increases, meaning that the object will require more force to initiate or overcome sliding motion. Conversely, if the normal force decreases, the frictional force will also decrease proportionally. This linear relationship illustrates that frictional force depends significantly on the normal force, reinforcing the concept that the two forces are linked in their effects on motion.