Classical Mechanics

The birth of modern physics began with investigations into one of the fundamental questions of natural philosophy — how and why do objects move?  For almost two thousand years, Aristotle's theories on the nature of motion were held unchallenged. The 16th century Italian polymath Galileo Galilei (1564 - 1642), through rigorous experimentation and mathematical analysis, finally overturned these many centuries of flawed understanding, fuelling the nascent Scientific Revolution.  Galileo, among others, set the stage for the English scientist Isaac Newton (1642 - 1727) to formulate the laws of motion which are the foundation of classical mechanics — the scientific study of motion and its causes.  Such was Newton's contribution to the development of classical mechanics, that it is often called Newtonian mechanics.

At the dawn of the 20th century, the theory of classical mechanics was so successful, that it was believed by many that our scientific knowledge was virtually complete.  A few minor details had to be ironed out, but essentially there was little left to discover. We now know that this was far from the case, with the formulation of the theories of quantum mechanics and general relativity.  Once again, our understanding was overturned. The theory of classical mechanics could not describe the behaviour of matter at very small scales (the atomic level), very large scales (planetary, stellar and galactic objects) or at speeds approaching the speed of light.  This may lead the reader to question ‘Why study classical mechanics?’  Shouldn't this field of study be consigned to the dustbin of history?  Classical mechanics, despite being an inaccurate theory, is a very accurate approximation of the behaviour of objects in our everyday experience.  So much so, that it still forms the theoretical basis for most branches of engineering. It is much simpler and easier to perform calculations within classical mechanics, as it provides solutions with sufficient accuracy without unnecessary complexity.

Classical mechanics may be partitioned into two sub-disciplines: kinematics and dynamics.  Kinematics, which is examined in the next section, aims to describe motion using a mathematical model.  It defines the concepts of velocity and acceleration, the ‘how’ of motion.  Dynamics, on the other hand, seeks to answer the ‘why’ of motion.  That is, what causes an object to move, and how can an object's movement be changed.  In this section, we discuss Newton's laws of motion, as well as his law of universal gravitation.