P01-020 – Particle Model

Particle Model

The description of the motion of an object if often complex, especially if one must account for the overall motion of the object (the path it appears to follow) as well as the motion of the object itself (rolling, twirling, etc.). As a way to ease into Kinematics, which seeks to describe the motion of an object without understanding the causes for the motion, we will at first neglect its shape and size treat it as a particle.

A particle has no size, no top nor bottom, no front nor back, and therefore the objects we will consider will either be point-like masses or will be treated as point-like masses. While this Particle Model fails to fully describe certain types of motion, it is a very good model to describe the overall motion of a solid as it moves along a path and makes for a manageable introduction to Kinematics. As a consequence, any object for which we will study the motion will be treated as a particle with all of its mass concentrated at a point.

As we advance through mechanics, we will eventually reach the limit of the Particle Model and will have to develop a better description for more advanced motions such a rotation and rolling. Until that point, however, we will continue to use the Particle Model consistently.