Some examples of frictional forces include the force between shoes and the ground when walking, the force between tires and the road while driving, and the force between a falling object and the air surrounding it. Many machines also involve the use of frictional forces.
Friction most commonly refers to the resisting force generated when two solid surfaces slide against one another. However, there is actually a wide variety of different types of friction that includes skin friction, fluid friction, internal friction, lubricated friction and dry friction. Each of these frictional energies has unique features and dynamics, but the overarching hallmarks of frictional forces remain the same.
When two touching surfaces slide against one another, complex interactions occur at an electromagnetic level between the surface's charged particles. These frictional forces convert the kinetic energy generated by their movements into heat. These same principles apply to objects moving through a liquid or through the air, creating different types of frictional energy. A frictional coefficient is computed by determining the ratio of the force of friction between two objects and the force that is pushing them together. Different combinations of surfaces have different frictional coefficients. The shape of an object does not influence fiction; the object's weight and the amount of force applied are the two affecting factors.