A curve of a force F, vs displacement x (F vs x), represents the magnitude of a force as it is producing a displacement of a body. The area under the curve froma point x1, to point x2, represents the work done by the force;W =⌠FdxIf the force is constant from x1 to x2, then; W =F∙(x2 - x1)The slope of the curve at a given value of x, (dF/dx),tells us how the force F isvarying with displacement x at that point.For the case of a constant force, the value of the slope is zero, (dF/dx=0),meaning that the force is not varying as the displacement takes place.