Rigid bodies and non-inertial frames

Abstract

We are now dealing with a special case of a many-particle system, albeit an idealization. A rigid body is understood as an assembly of particles interacting with forces that are so’ stiff’ that the separation between any two particles remains constant. From the considerations of the previous chapter we know that these internal forces do not affect the dynamics of the body. What distinguishes a rigid body from a point mass is its extension in space. This means that it must be described by its orientation as well as its location, i.e. six variables rather than three. Our task in the following sections must be to identify suitable variables to use, and to set up equations of motion for them in order to describe the change of these variables.