TABLE OF CONTENTS When we were carrying on our wind-tunnel work we had no thought of ever trying to build a power aeroplane. We did that work just for the fun we got out of learning new truths. Orville Wright, 1928 (in Kelly, 1996)
In the early twentieth century Albert Einstein revolutionised theoretical physics by overturning Newton's view of gravity. With it went Newton's view of the universe as permanent and unchanging. Although Einstein himself resisted it, the equations seemed to predict a dynamic universe. Stephen Hawking, 1999
Mechanics is the science of forces acting on bodies at rest and on bodies in motion. The whole of mechanics is subdivided into statics, kinematics and dynamics.
Statics deals with forces on bodies at rest and in general addresses the equilibrium of these forces by both external and internal reactions.
Kinematics is the study of the relative motion of one or more connected or disconnected bodies or particles, without any reference to forces acting on them.
Dynamics is the study of forces acting on bodies in motion.
As a helpful introduction to this aspect of mechanics we examine the types of forces and combinations of forces that can act on bodies or systems of bodies. We often talk about forces, but we equally often overlook the fact that a force is not an easily measured quantity. In fact in a most general way the concept (idea) of a force is based entirely on the "effect" it can create.
