Start with the basics - the fundamentals of physics that all students of physics start with. Equivalent to an introductory course in physics.
How things move though space. Learn how point objects move though both one-dimensional space, and two-dimensional space.
What causes things to move through space. Learn about the phenomena that affects the motion of objects through space.
The 'thing' that does work on an object. It makes things move, and is what makes the universe run at all scales, from the quantum to the astronomical.
Momentum is what keeps an avalanche roll once it has been set off - once moving, it takes a large external force to stop!
Simple Harmonic Motion
Anytime there is something moving back and forth repeatedly in a consisten pattern, you have simple harmonic motion. Think of a pendulum.
What happens when you have a system of objects interacting with each other through simple harmonic motion? You have waves.
Different from point objects - think of so many point objects that they blend into one system known as a fluid. Or, you can just think about water.