Abique, Clarisse Anne N.
BSCE-2A
Statics of Rigid Bodies
Assignment 1
Explain thoroughly the type of forces (9 forces in the summary of terms) by giving an example of each force with
explanation and pictures.
1. COPLANAR FORCES –A force system is said to be coplanar if all of the force's lines of action fall within a
single plane.
Coplanar force structure refers to the
number of forces that stay in a similar plane. If a
body is beneath the action of numerous forces and
all the forces lie in a similar plane, they are said to
be coplanar forces. So, when some forces act on a
body, they are called a force system or a system of
forces. It is also stated as the number of forces in a
structure that remains in a single plane. Consider
the man pulling the stone with the rope. Several
forces are acting on the stone: tension in the rope,
the usual reaction offered by the surface, the
frictional force, and the self-weight of the stone
acting downwards. All these forces lie in the same
plane, forming a coplanar force system.
2. COLLINEAR FORCES - When the line of action of forces is acting along the same line for a system, such
force is defined as the collinear force.
Tug of war is a contest in which two teams pull
at opposite ends of a rope until one drags the other over a
central line. In a tug of war, all of forces applied by the
people towards them are along a line, along the length of
the rope. These two forces are called action and reaction
forces and are the subject of Newton's third law of
motion. In this activity, the rope is the means to transfer
forces. The first team to tug is the action force, causing
the pull on the rope, as the reaction force, the other teams
rope end "feels" the pull. Therefore, it is an example of a
collinear force.
3. CONCURRENT FORCES - A force system is said to be concurrent if the lines of all forces intersect at a
common point. Concurrent forces are two or more forces whose lines of accomplishment intersect at a similar
point to cause rotation. The forces do not essentially have to be applied.
A typical concurrent force situation is a lifting eye. The
pulling forces in any cables must pass through the center
of the eye. If only one eyebolt (correctly positioned over
the center of gravity) and the load is suspended, the bolt
force must pass through the exact center.
4. NON-CONCURRENT FORCES - are two or more forces whose magnitudes are equal but act in opposite
directions with a standard line of action.
Non-concurrent force means that when the forces acting
on an FBD do not intersect at a common point, the system
of forces is said to be non-concurrent. For example, when
a cyclist pedals, his or her feet are parallel. One foot
pushes a petal forward while the other pushes the other
pedal backward. These two forces cause the wheels on the
bike to rotate.
5. PARALLEL FORCES - forces that act in the same or opposite directions at different points on an object.
Forces that are not concurrent and their lines of
action are not the same and parallel to each other, then the
forces are called parallel forces—for instance, children
sitting on a seesaw. The children are applying the two
forces at the ends, and the fulcrum in the middle gives the
counter force to maintain the seesaw in a neutral position.
6. ACTION FORCE – these are forces that are applied to a body.
Newton's Third Law of Motion states, "When one
object exerts a force on a second object, the second
one exerts a force on the first that is equal in
magnitude and opposite in direction." When a ball
is thrown on the floor or a wall, it bounces back.
The force exerted by the ball on the ground or wall
is the action force. The force that the ground or
wall exerts on the ball in response to the action
force causes the ball to jump or bounce back. This
force is nothing but the reaction force.
7. REACTION FORCE – these are forces that are developed by free bodies upon another bodies.
Reaction forces and reaction moments are
usually the results of the actions of applied forces.
Friction is the reaction force resulting from surface
interaction and adhesion during sliding. For example,
when a person sitting on a chair pushes the wall with his
feet, the chair moves backward. The motion of the chair
cannot exist without the existence of a force. Therefore,
the force responsible for moving the chair is the reaction
force. The reaction force is continually exerted in the
opposite direction of the action force. Hence, the chair
moves in a backward direction.
8. TENSION FORCE - forces that tend to move away from the body or elongate the body.
Tension is the force transmitted through a rope,
string, or wire when pulled by forces acting from opposite
sides. For example, a crane uses a long metallic chain and
a big pulley while lifting objects. Since the object and the
operator are not in direct contact, the force required for
lifting reaches the object indirectly through the tension
force possessed by the chain. This is one of the significant
applications of the tension force in the industrial world.
9. COMPRESSION FORCE - forces that tend to move away from the body or elongate the body.
A sponge is one of the best examples of
compression force in real life. The sponge has
an elastic structure, which is why it can regain
its original shape as soon as the effect of the
externally applied force fades away. When a
push force is applied across both ends of the
sponge, it tends to squeeze, and the original
size of the sponge gets reduced. Hence, a
compression force is said to be present.