Force is a vector quantity.
When two or more forces act on an object the net force is also a vector. This vector, in mathematical terms called the resultant, and is the vector sum of the vectors. Any vector can be described as the sum of a set of orthogonal, or linearly independent vectors. Typically engineers define the unit vectors in the x, y, and z directions as respectively. Thus the vector shown in Figure 1 can be written as, The components of the sum of two or more vectors is found by adding up the sum of the components.