Overview

  Physics tries to understand the world around us. It differs from other sciences such as biology and chemistry, in the way it approaches problems. It attempts to understand things from at a more fundamental level. If you want to ask a question in physics ask ``why" enough times and you'll get a physics question. For example, the question

• ``Why doesn't Gary like me?'' Because you have bad breath
• ``Why do I have bad breath?'' Because you eat too much garlic
• ``Why does garlic cause bad breath?'' Because garlic contains a chemical that smells bad
• ``Why do some chemical smell bad?" Certain chemicals bind to receptors inside the noise which send a message to the brain, which then interprets and decides among other things if it likes the smell or not
• ``Why do certain chemicals bind specifically to certain receptors?''

At this point, the answer will have to involve concepts in physics. A vague answer would be: Because the forces between the electrons and nuclei that make up the molecules and the receptor sites favor them binding together. To understand this in more detail, it is necessary to understand how electrons and nuclei interact with each other. Physicists have studied such questions quite extensively and give quite good answers to these questions.

If you get down to fundamental questions, such as how electrons interact, physics can give extremely accurate answers. However if you ask a more general question, like why it is that most people don't like fish-flavored cheese cake, then physics is pretty hopeless. In principle such a question could be understood from a fundamental, physics point of view, but it would be far far too complicated to answer it. Your brain is make up of electrons, protons and nuclei so in principle it should be possible to understand it's workings if you knew exactly how your brain was constructed (which we don't).

In some sense, we're really quite lucky that things at a fundamental level are so easily understood. When I say easily understood, I don't mean that I can tell you the laws of physics, and then you'll understand all of physics. To do that would require a lot more math then you probably know at present. It would also require an intuitive understanding of physical concepts that take most people many years to acquire. All that I mean is that you can write down a set of equations, which in principle tell you how particles evolve in time. These equation are really not that complicated. You can write them down in a page or so. To solve these equations, in the case of the brain, or even in the case of three electrons and one proton, can be extremely difficult. There is a big difference in knowing how in principle something works and figuring out what it's going to do.

To start with we're going to study classical mechanics. It's a good subject to start with. It deals with the motion of big objects, such as baseballs, blocks, cars, or even people flying through the air. Big objects like this obey classical mechanics to a ridiculously good approximation. It's nicer to start with than electricity and magnetism because it's less mysterious. If you drop something you can actually see it fall, where as electricity is slightly more difficult to conceptualize. Hopefully you'll study electricity and magnetism in the third part of this sequence.

Classical mechanics illustrates fundamental notions about physics. How starting from simple equations, you can deduce, with no other assumptions, how a system will behave. To do this, we'll first have to get a grip on ``units''.