AP Physics Unit Symbols Table: All Four Courses

Every unit symbol on any AP Physics sheet

This is the UNIT SYMBOLS box, which sits next to the prefixes table on the first page of the Table of Information. It answers one question only: what unit does this abbreviation stand for. If you want to know what an italic letter in an equation means, that is the variable symbol table instead, and the two tables share letters without sharing meanings.

Nineteen distinct symbols appear across the four booklets. No booklet prints all nineteen.

The booklets list their own symbols alphabetically by unit name, which is why ampere comes first and watt comes last on the longer tables. AP Physics 1 and C: Mechanics use a two-column layout that reads across rather than down, so the order looks scrambled on the page even though it is the same alphabetical list.

What each course actually prints

AP Physics 1: eight symbols. hertz, newton, joule, pascal, kilogram, second, meter, watt. That is the complete box.

AP Physics C: Mechanics: seven symbols. hertz, newton, joule, second, kilogram, watt, meter. The same as Physics 1 with pascal removed, because C: Mechanics has no fluids unit and therefore no pressures.

AP Physics C: Electricity and Magnetism: fifteen symbols. ampere, coulomb, electron volt, farad, henry, hertz, joule, kilogram, meter, newton, ohm, second, tesla, volt, watt.

AP Physics 2: eighteen symbols. ampere, coulomb, degree Celsius, electron volt, farad, hertz, joule, kelvin, kilogram, meter, mole, newton, ohm, pascal, second, tesla, volt, watt.

Two structural facts fall out of those four lists, and both are worth having.

C: Mechanics prints exactly the symbols that all four courses share. Its seven are the intersection: hertz, joule, kilogram, meter, newton, second and watt appear in every booklet, and nothing else does. So the smallest table is not an arbitrary subset, it is the common core.

Henry is on the C: Electricity and Magnetism table and nowhere else. It is the one unit in the whole set that AP Physics 2 does not print, and it is there because inductance is a C: E&M topic that the algebra-based course does not carry. If you are working with an inductor and an $L$ measured in henrys, you are in C: E&M.

The three symbols that are not what they look like

$\Omega$ for ohm. It is a capital Greek omega, not a zero, not a horseshoe and not the letter O. Written by hand it needs a flat base so it does not read as a zero. On the same sheet, lowercase $\omega$ is angular frequency, which is a different quantity entirely and never a unit.

mol for mole. Three letters, no period, and it is the only unit symbol on any of the four tables longer than two characters. AP Physics 2 prints Avogadro's number as $6.02 \times 10^{23}\ \text{mol}^{-1}$, using the symbol as an exponent-bearing unit rather than a word.

eV for electron volt. Lowercase e, uppercase V. It is a unit of energy, not of potential, despite the V. An electron volt is the energy an elementary charge picks up moving through a potential difference of one volt, which is why the two are related and why the abbreviation is confusing. It appears on the Physics 2 and C: E&M tables, and both of those booklets also print the conversion $1\ \text{eV} = 1.60 \times 10^{-19}\ \text{J}$ in the constants box.

Worth adding: kg is the SI base unit of mass, not g. The prefixed form is the base unit, which is unique in SI and the reason kilogram appears on every one of the four tables while gram appears on none of them.

Unit symbols that collide with variables on the same sheet

The UNIT SYMBOLS table and the variable definition lists sit within a few pages of each other in the same appendix, and eleven letters appear in both, meaning two different things. Upright roman type is a unit; italic type is a variable. That distinction is real in the booklet and invisible in most students' handwriting.

The pairs that actually cost points are these three.

J. A joule is energy. Italic $J$ is impulse on the mechanics list, in $\text{N} \cdot \text{s}$, and current density on the C: Electricity and Magnetism electricity list, in $\text{A}/\text{m}^2$. Three unrelated things.

K and T. Kelvin is the unit of temperature; italic $K$ is kinetic energy on every mechanics list. Meanwhile italic $T$ is period on the mechanics lists and temperature on the AP Physics 2 thermal list, while the unit symbol T is the tesla and the prefix T is tera. "$T = 300\ \text{K}$" is a temperature and "$T = 0.30\ \text{s}$" is a period, and the only thing telling them apart is the unit that follows.

W and V. A watt is power and italic $W$ is work, which are related but not equal: power is work per unit time, so writing $W$ for both in the same line of algebra will produce nonsense. Similarly a volt is the unit and italic $V$ is the quantity, electric potential, except in the C: E&M electricity list where the sheet explicitly defines $V$ as "electric potential or volume".

The habit that fixes all of this: write units after a number and variables before an equals sign, and never let a unit symbol appear on its own in the middle of an algebraic expression.

Where the derived units come from

Only four of the nineteen are SI base units: the kilogram, the meter, the second and the ampere. Two more, the kelvin and the mole, are base units of SI that the AP courses treat as ordinary givens. Everything else on the table is built from those, and the sheet expects you to be able to unpack them when a unit check goes wrong.

The booklet does not print this second table. It gives you the abbreviation and the name and stops. The decompositions above follow from the equations that are printed: the volt is joules per coulomb because $\Delta U_E = q \Delta V$, the ohm is volts per amp because $I = \Delta V/R$, the farad is coulombs per volt because $C = Q/\Delta V$, and so on. If you ever forget one, find the equation that defines the quantity and read the unit off it.

Hertz is the one to watch. It is inverse seconds, and the sheet prints $T = 1/f$ to say so. A frequency in Hz multiplied by a time in seconds is a pure number, which is exactly what you need inside $x = A\cos(2\pi f t)$.

Reading the box on exam day

This is the least useful table in the appendix for most students, and that is fine. If you already know N is newton, you will never look at it.

It earns its space in two situations. One: a multiple choice question offers answers in units you half recognize, and you need to confirm that T is tesla and not something else before eliminating. Two: you are checking an answer by unit analysis, the result comes out in $\text{kg} \cdot \text{m}^2/\text{s}^3$, and you want to know whether that has a name. It does, it is the watt, and the box confirms W is on your course's list, which tells you the question expects an answer in power.

What the box will not do is tell you what an italic letter in an equation means. That is a different table, printed beside the equations rather than in the information box, and it is the one worth reading properly.