ABSTRACT
A force is something that is capable of changing an object's state of motion, that is, changing its velocity or producing an acceleration. Since a force can produce an acceleration – a vector quantity – force must itself be a vector quantity, with both magnitude and direction. A force is applied to a moving block when it reaches the origin, and the block then begins to deviate from its straight-line path. With the force at an angle to the initial motion, it would appear that the solution is complicated. Newton recognized that in any force application, there is always a mutual interaction; therefore, forces occur in pairs. In illustrations of physical situations, sometimes called space diagrams, force vectors are drawn at different locations to indicate their points of application. If the forces are summed both vertically and horizontally, they independently should add to zero.
