Physics Edition. Every famous formula in physics is just constants and variables waiting for numbers. Today you plug real values into fifteen of the most famous formulas in physics and watch the universe do arithmetic.
In physics, a variable is a letter standing in for a measurable quantity, mass, velocity, charge, time. A constant is a number the universe itself has fixed, the same everywhere, in every problem. Substitution means swapping the letters for real measurements and doing the arithmetic. Do that correctly and the formula stops being an abstraction; it becomes a prediction you can check against the real world.
The one rule: replace every copy of a variable with your number, keep the constants exactly as they are, then compute. Units travel with the numbers — a force answer is only correct if it's in newtons.
Part 2 · Know Your Parts
Constants, coefficients, and variables
Before plugging in, learn to spot each kind of piece. Take Kinetic Energy, — three different roles working together.
Variable
A quantity that changes from problem to problem. In , is velocity — you measure or choose it.
Coefficient
A fixed multiplier baked into the formula's derivation. In , comes from calculus, not measurement — it never changes.
Physical Constant
is Earth's gravitational acceleration. It shows up in and the pendulum formula — always the same value, everywhere on Earth.
Physics has more named constants than geometry ever did. for gravity near Earth's surface, for universal gravitation, for Coulomb's law, for the speed of light, for the ideal gas law. Every one of them was measured once, by someone, and now belongs in every formula that needs it.
Part 3 · Warm Up
The Substitution Machine
Pick a formula below to see what it represents, set the value with the slider, and watch every substitution step in proper math. Constants stay put while variables get replaced.
Substitution Machine Foundations
Violet = variable · Amber = plugged-in value · Green = result · Teal = constant
Part 4 · Formula Browser
Explore all fifteen formulas
Tap any formula to see what it models, what each letter means, and a live substitution you can drive with the sliders. Variables in violet, constants in teal, coefficients in amber.
Interactive Formula Browser Advanced
Click a formula card, then move the sliders to plug in values.
Notice the pattern: every formula, no matter how famous, is just constants and coefficients combined with variables. Plug in the variables — the rest is arithmetic.
Part 5 · Mechanics Explorer
Forces, motion, and energy
Nine formulas that describe how things move and how they trade energy back and forth. Slide the values, watch the diagram redraw, and follow the substitution live.
Mechanics Explorer Advanced
Part 6 · Fields, Waves & Modern Physics
Beyond mechanics
Six formulas that reach further: gravity across space, charge, current, gas, sound and light, and Einstein's most famous equation. Same substitution move, bigger stage.
Fields & Modern Physics Explorer Advanced
Part 7 · Show What You Know
The Plug-it-In Physics Challenge
A scenario, a formula, and some measurements. Substitute and solve. Watch the units in the prompt — they tell you what to plug in and what to expect back.
Plug-it-In Challenge All 15 Formulas
Difficulty:
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Walk Away With This
Swap the letter. Do the math. Every time.
From Newton's second law to Einstein's most famous equation, every one of physics' greatest formulas is just variables waiting for measurements. Constants stay fixed. Coefficients scale. Variables get replaced. That one move is how physics turns into prediction.