A force has four (4) attributes viz: magnitude, direction, point of application and sense.
- The magnitude of a force is the size of the force and this size is measured in Newton (N).
- The direction of the force is the direction of the line along which it acts either vertically or horizontally.
- The point of application is the point of contact between bodies exerting forces on each other.
- The sense is indicated by the way it act along a line of action of force, for instance, upwards, downwards, to the left or to the right and the sense is generally denoted by an arrow.
Types of force systems (the arrows represent the forces)
(1) Coplanar Forces – these are forces which lie on the same plane parallel to the line of action of the force (see Figure 1).
(2) Non-coplanar Forces – these are forces that do not lie on the same plane (see Figure 2)
(3) Concurrent Forces – this occurs when the action lines of all the forces of a system intersect at a common point (see Figure 3).
(4) Non-concurrent Forces – this occurs when the line of action of the forces do not intersect at a common point (see Figure 4).
(5) Parallel Forces – this is a special case of non-concurrent forces in which the lines of action of the forces are parallel to each other (see Figure 5).
(6) Collinear Forces – this is a special case of coplanar and concurrent force system in which all forces act along a single line of action (see Figure 6). The common example of collinear forces is the tug of war sporting event.
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