# UCD: Physics 9HA – Classical Mechanics


• Preface
The whole idea of the study of physics is to understand how the universe operates. We cannot actually ever know for sure how this works, but we play a sort of game: We develop a model that explains why things happen the way they do, and then we test the effectiveness of that model when it comes to predicting how other things will unfold. If the model predicts accurately, it is a “good” model, and if it doesn’t, it is discarded.
• 1: Motion
The most fundamental concept in physics is motion. Here we will examine motion progressing from its simplest manifestation to more advanced forms, growing our mathematical toolbox along the way.
• 2: Force
Our study of motion was an examination taught us about the results of actions. We now begin our exploration of what causes various types of motion.
• 3: Work and Energy
Using Newton's laws to solve every problem in mechanics can be quite cumbersome. Some problems don't require the degree of detail that force analysis gives, which makes it possible to develop and use shortcuts to their solutions. In our search for such a shortcut, we end up encountering one of the most fundamental and profound principles in all of physics.
• 4: Linear Momentum
We continue our search for shortcuts to solving problems for which the direct use of Newton's laws are inconvenient. In the case work/energy, we found such a shortcut using Newton's 2nd Law, limiting it to the direction of motion. Here we turn to Newton's 3rd Law for inspiration, and encounter another important conservation principle.
• 5: Rotations and Rigid Bodies
Up to this point, we have treated objects as points whose motion is limited to translation through space. We now extend our analysis to extended rigid objects that can rotate around a fixed point.
• 6: Angular Momentum
We have already seen that whatever we did for linear motion can be expanded to rotational motion. A particularly useful and interesting application of this is angular momentum, which – you guessed it – also comes with an important conservation law.
• 7: Gravitation
With the fundamentals of classical mechanics firmly in hand, we employ the tools we have developed to the most celebrated of the fundamental forces, following in the footsteps of Kepler and Newton.
• 8: Small Oscillations
All around us we see examples of restoring forces. Such forces naturally result in motion that is oscillatory. We will look at what these physical systems have in common.
• Front Matter
• Back Matter

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