⚡ Physics

Introductory physics is mostly a small set of relationships applied over and over in different situations, which is why it's worth learning the formulas properly rather than memorizing plugged-in numbers for one specific problem. This section covers classical mechanics (Newton's Second Law, momentum, speed), energy and work (kinetic and potential energy, work, power, and the famous mass-energy relationship), and electricity (Ohm's Law) — the formulas that show up across a typical introductory or AP-level physics course.

Physics formulas are easy to memorize and hard to apply correctly, because the difficulty is usually in figuring out which variables you actually have and which you're solving for — not the algebra itself. That's why every page here pairs the formula with a real worked example showing exactly which values go where, a list of the mistakes students make most often with that formula (unit mismatches and sign errors are the two most common), and a calculator for checking your own substitutions once you understand the setup.