Application of Newton's Laws
TYPES OF FORCE
TYPES OF FORCE
When determining how an object reacts to a force or forces, it is important to
understand the different types of forces that may act on the object.
DEFINE the following:
EXPLAIN the difference between a static-friction force and a
STATE two factors that affect the magnitude of the friction force.
difference between centripetal force and
The previous section discussed the equilibrium of forces as they act on bodies. Recalling that
a force is defined as a vector quantity that tends to produce an acceleration of a body in the
direction of its application, it is apparent that the student must be acquainted with the various
types of forces that exist in order to construct a correct free-body diagram and apply the
appropriate equation. A force is applied either by direct mechanical contact or by remote action.
Tensile and Compressive Forces
In discussing the types of forces, a simple rule is used to determine if the force is a tensile or a
compressive force. If an applied force on a member tends to pull the member apart, it is said to
be in tension. If a force tends to compress the member, it is in compression. It should also be
mentioned that ropes, cables, etc., that are attached to bodies can only support tensile loads, and
therefore such objects are in tension when placed on the free-body diagram. In addition, when
a fluid is involved, it should be understood that fluid forces are almost always compressive
Another type of force often used in classical physics is the force resulting from two surfaces in
contact, where one of the surfaces is attempting to move parallel to or over the other surface.
Such forces are referred to as friction forces. There are two types of friction forces: those due
to dry friction, sometimes called Coulomb friction, and those resulting from fluid friction.