Lastly, Newton’s Third Law
of Motion states that for every action, there is an
equal and opposite reaction (Physics
Classroom). This action and reaction can be
demonstrated by any object on Earth, for example a chair
that is at rest has a downward force of gravity which
will be equal, but opposite of the normal force of the
ground to the chair acting upward. Newton observed that
forces always come in pairs of the action force and
reaction. Knight outlines the requirements of a force as
follows, push or pull, acts on an object, requires an
agent, is a vector, and is either a contact force or
long range force (2013, p. 117). A contact force is a
force that only occurs when there is contact such as
normal, tension, thrust, and friction forces. Long range
forces are forces that act on an object without physical
contact, this includes forces such as electric,
magnetic, and gravitational forces.
