In physics, we seek to understand the properties and behaviors of the world at all levels of scale. What are the constituents, and how do they interact?
We observe, experiment, and build conceptual models. We build models on many different levels of scale. Theories are grand models that embrace a huge range of phenomena. Theories cannot be proved absolutely. If physicists have a lot of confidence in a theory, then its key features are referred to as laws.
Models are made by people for people. One must be careful not to confuse the model with the reality. A model is just a simple, manageable representation. Models can change as knowledge changes, but the underlying reality presumably does not change. The medium physicists use to create their models is usually mathematics. Different physical models have different ranges of applicability, they have been verified to work on different scales. The science of Physics is often divided into Classical Physics and Modern Physics.
In this class we will mostly study Classical Physics. Classical Physics in a model of the macroscopic world around us. All the laws of classical physics were known by the end of the 19th century. The known properties of matter at the end of the 19th century were mass and charge. The smallest constituents were atoms. The known interactions were gravity, modeled by Newton's law of gravitation, electromagnetic interactions, modeled by Maxwell's equations, and contact force arising from the requirement that "atoms need their space". Consequences of the interactions were described by Newton's laws of motion, which predict how matter behaves when acted on by forces. Statistical physics and thermodynamics were developed for describing systems with a large number of degrees of freedom, when it becomes impossible to keep track of the individual constituents.
Classical physics works well describing and predicting almost all everyday phenomena. It breaks down when things get too ... . (You can substitute here almost any very large deviation from out everyday experience.)
Most disciplines have their own special vocabulary. The vocabulary of physics includes words whose meaning in everyday language may depend on the context in which they are used. In physics, these words have only one precisely defined, context-independent meaning.
Take, for example, the word "force".
Only the first of these three sentences uses the word "force" to refer to the concept it describes in physics.
Words such as position, velocity, acceleration, energy, power, etc, all have context-dependent meaning in everyday language. It is important that when communicating about physics, you always use the precise, context-independent definition of these words. Words whose definitions you should keep in mind appear in bold red font in the Web material.