ABSTRACT
In Fig. C5.3, two co-planar (occupying the same plane), forces act on an object and the object does not move. Hence, there must be a third force that acts (unless the forces applied are equal and opposite) in order to maintain equilibrium. To calculate the third force, the resultant (one force that would have the equivalent effect of the two forces, i.e., the sum of two or more vectors (having both magnitude and direction)) of the two forces must be determined. This can either be solved graphically (by drawing a scaled diagram) or mathematically by resolving the forces and then using the first condition of equilibrium (∑F = 0) to determine the third force (the force needed to maintain equilibrium).
