Kinetics of Rigid Bodies

Abstract

If we all worked on the assumption that what is accepted as true is really true, there would be little hope of advance. - Orville Wright (1871–1948) U.S. Inventor Who, with His Brother Wilbur Wright, Achieved the First Powered, Sustained, and Controlled Airplane Flight. Until now we have been concerned with the kinetics of particles, i.e., the kinetics of objects that have nonzero finite mass but do not occupy any physical space. Furthermore, in Section 2.15 of Chapter 2 we studied the kinematics of motion of a rigid body. In this chapter we turn our attention to the kinetics of rigid bodies. To this end, the objectives of this chapter are threefold: (1) to describe quantitatively the forces and moments that act on a rigid body; (2) to determine the motion that results from the application of these forces and moments using postulated laws of physics; and (3) to analyze the motion. The key difference between a particle and rigid body is that a particle can undergo only translational motion whereas a rigid body can undergo both translational and rotational motion. In general, for motion in ℝ 3 it is necessary to specify three variables for the translational motion and to specify another three variables for the rotational motion of the rigid body.