AP Physics Exam Conventions: All Four Courses

Every AP Physics exam prints a short list of assumptions you may use without justifying them. The four courses print different lists. AP Physics 1 prints four bullets, AP Physics 2 prints nine, AP Physics C: Mechanics prints three, and AP Physics C: Electricity and Magnetism prints seven.

Not tied to one unit. The conventions box is printed in the Table of Information appendix of all four course and exam descriptions, effective Fall 2024, version 1: printed page 211 of AP Physics 1, page 218 of AP Physics 2, page 204 of AP Physics C: Mechanics, and page 178 of AP Physics C: Electricity and Magnetism. Bullet counts are 4, 9, 3 and 7 respectively, and the sixteen distinct bullet texts are quoted in full on this page.

Where the conventions box sits, and what it claims

Each course and exam description ends with a Table of Information appendix: constants, prefixes, unit symbols, trigonometric values, geometry, and a small ruled box of conventions. That box is the subject of this page.

The four boxes are printed on these pages of the current course and exam descriptions, all of them effective Fall 2024, version 1:

Course	Printed page of the CED	Bullets in the box
AP Physics 1: Algebra-Based	211	4
AP Physics 2: Algebra-Based	218	9
AP Physics C: Mechanics	204	3
AP Physics C: Electricity and Magnetism	178	7

The box is not a study note. Its opening line in every course begins "The following conventions are used in this exam", so it is a statement about the exam itself rather than about the course. A sample free-response question in the AP Physics 1 CED (printed page 186) tells students to "Begin your derivation by writing a fundamental physics principle or an equation from the reference information", which is the CED confirming that reference material of this kind is in front of you while you write.

The rest of this page quotes each box in full, then sets the four side by side.

AP Physics 1: four conventions

The heading reads "The following conventions are used in this exam:" and each bullet carries its own escape clause.

The frame of reference of any problem is assumed to be inertial unless otherwise stated.
Air resistance is assumed to be negligible unless otherwise stated.
Springs and strings are assumed to be ideal unless otherwise stated.
Fluids are assumed to be ideal, and pipes are assumed to be completely filled by fluid, unless otherwise stated.

The fluids bullet is the one no other course prints, and it is there because Unit 8, Fluids belongs to AP Physics 1 alone. It does two jobs at once: it makes the fluid ideal, which is what lets you use Bernoulli's equation and the continuity equation without arguing for them, and it makes the pipe full, which is what lets you treat the cross-sectional area of the pipe as the cross-sectional area of the flow.

Notice what is missing. Surface friction is not switched off. AP Physics 1 grades kinetic friction and static friction directly under Topic 2.7, so the box assumes away air resistance and leaves friction between surfaces to the question.

AP Physics 2: nine conventions

AP Physics 2 moves the escape clause into the heading, which reads "The following conventions are used in this exam unless otherwise stated:". Every bullet under it is then stated flatly.

The frame of reference is inertial.
Frictional forces are negligible.
Strings, springs, batteries, wires, and meters are ideal.
Resistors and lightbulbs are ohmic.
Ideal gases are monatomic.
The electric potential is zero at an infinite distance from an isolated point charge.
Current is conventional current.
Capacitors are air-filled $(\kappa = 1.0)$ .
The small angle approximation is valid for single- and double-slit diffraction.

This is the longest of the four boxes, and every bullet past the third is doing work that the algebra-based second course specifically needs. Bullet 5 is the one worth memorizing: monatomic is why the AP Physics 2 equation sheet prints internal energy as

U = \frac{3}{2}nRT = \frac{3}{2}Nk_BT

with the factor $3/2$ already fixed, and why average kinetic energy per particle appears as $K_{avg} = \frac{3}{2}k_BT$ . A diatomic gas would carry $5/2$ in both places, and the sheet gives you no way to write that.

Bullet 8 sets the dielectric constant to 1.0, so a parallel plate capacitance question defaults to $C = \varepsilon_0 A/d$ even though the sheet prints the more general $C = \kappa \varepsilon_0 A/d$ . Bullet 9 is the licence to write $\sin\theta \approx \tan\theta \approx \theta$ in radians when you handle double-slit interference and single-slit diffraction.

AP Physics C: Mechanics: three conventions

The shortest box of the four, and the only one whose heading ends in a full stop rather than a colon: "The following conventions are used in this exam."

The frame of reference of any problem is assumed to be inertial unless otherwise stated.
Air resistance is assumed to be negligible unless otherwise stated.
Springs and strings are assumed to be ideal unless otherwise stated.

These are word for word the first three bullets of the AP Physics 1 box. C: Mechanics simply does not print the fluids bullet, and it has no fluids unit to print it for.

The air resistance bullet deserves a second look in this course specifically, because C: Mechanics is the only one of the four with a topic devoted to resistive forces, Topic 2.9, where velocity-dependent drag and terminal velocity are the whole point. That is not a contradiction. The bullet says "unless otherwise stated", and a question that hands you a drag force of the form $F_d = -bv$ has stated otherwise in the clearest possible way.

AP Physics C: Electricity and Magnetism: seven conventions

The heading matches AP Physics 2: "The following conventions are used in this exam unless otherwise stated:".

The frame of reference for any problem is inertial.
Frictional forces and air resistance are negligible.
Strings, springs, batteries, wires, and meters are ideal.
The electric potential is zero at an infinite distance from an isolated point charge.
The direction of current is the direction in which positive charges would drift.
Resistors and lightbulbs are ohmic.
Capacitors are air-filled $(\kappa = 1.0)$ .

Bullet 4 is the boundary condition that makes every absolute potential in the course well defined. Without it, only potential differences would have meaning, and $V = \frac{1}{4\pi\varepsilon_0}\frac{q}{r}$ would be one member of a family of answers differing by a constant.

Bullet 5 is the same idea as AP Physics 2's "Current is conventional current", written the long way. Both give you conventional current, and neither asks you to reason about electrons drifting the other way unless a question raises it.

What C: E&M does not print, and AP Physics 2 does, is the ideal-gas bullet and the small-angle bullet. Neither course topic exists here.

All sixteen bullets, and which course prints each

Across the four booklets there are sixteen distinct bullet texts. The table below is that full set, quoted exactly, with a mark in each column that prints it. The four column totals are 4, 9, 3 and 7, which is 23 marks in total, and every one of the sixteen rows carries at least one.

Bullet, as printed	P1	P2	C: Mech	C: E&M
---	:-:	:-:	:-:	:-:
The frame of reference of any problem is assumed to be inertial unless otherwise stated.	yes		yes
The frame of reference is inertial.		yes
The frame of reference for any problem is inertial.				yes
Air resistance is assumed to be negligible unless otherwise stated.	yes		yes
Frictional forces are negligible.		yes
Frictional forces and air resistance are negligible.				yes
Springs and strings are assumed to be ideal unless otherwise stated.	yes		yes
Strings, springs, batteries, wires, and meters are ideal.		yes		yes
Fluids are assumed to be ideal, and pipes are assumed to be completely filled by fluid, unless otherwise stated.	yes
Resistors and lightbulbs are ohmic.		yes		yes
Ideal gases are monatomic.		yes
The electric potential is zero at an infinite distance from an isolated point charge.		yes		yes
Current is conventional current.		yes
The direction of current is the direction in which positive charges would drift.				yes
Capacitors are air-filled with dielectric constant 1.0.		yes		yes
The small angle approximation is valid for single- and double-slit diffraction.		yes

The capacitor row is written out in words here because the booklets print it with the symbol: "Capacitors are air-filled $(\kappa = 1.0)$ ."

Two counting facts fall straight out of the table. No bullet text is printed by more than two of the four courses. Nine of the sixteen rows carry a single mark and the other seven carry two, and 9 plus 14 is the 23 marks the column totals demand. Every course states the inertial-frame idea, but AP Physics 1 and C: Mechanics write "of any problem is assumed to be", AP Physics 2 writes the bare "The frame of reference is inertial", and C: E&M writes "for any problem is", so even that one splits into three texts.

Second, every shared row pairs the same two courses. Three rows are shared by AP Physics 1 and C: Mechanics: inertial frame, air resistance, springs and strings. Four rows are shared by AP Physics 2 and C: E&M: ideal strings, springs, batteries, wires and meters; ohmic resistors and lightbulbs; zero potential at infinity; air-filled capacitors. Those are the only two pairings that occur. The four booklets fall into two families along subject-matter lines rather than along algebra-versus-calculus lines: the two mechanics booklets share their wording with each other, and the two electricity booklets share theirs with each other.

The wording differences that change what is guaranteed

Three differences are worth more than a footnote.

Where "unless otherwise stated" sits. AP Physics 1 and C: Mechanics attach it to each bullet. AP Physics 2 and C: E&M put it once in the heading. The practical effect is the same, but the algebra-based first course leaves you nothing to interpret, while the other two require you to carry the heading down onto every line.

Air resistance is not the same as friction. AP Physics 1 and C: Mechanics assume away air resistance and say nothing about surface friction. AP Physics 2 assumes away "frictional forces" and says nothing about air resistance. C: E&M is the only booklet that names both in one bullet. If you are writing a curriculum document, do not flatten these into one row.

Ideal means different things per course. In AP Physics 1 and C: Mechanics, the ideal-object bullet covers springs and strings only. In AP Physics 2 and C: E&M it also covers batteries, wires, and meters, which is what lets a circuit question hand you an ideal battery with no internal resistance, an ammeter with no resistance, and a voltmeter that draws no current, all without a word of setup.

What the conventions box does not do

The lists above are the complete contents of each box. Several things that get attributed to the conventions box are not in it.

The value of g. It sits one table up, under Constants and Conversion Factors, printed as $g = 9.8 \text{ m/s}^2$ and $g = 9.8 \text{ N/kg}$ . It is a constant, not a convention. The AP Physics 1 CED separately says elsewhere that the exam will use about 10 for numerical work, which the guide on whether g is 9.8 or 10 quotes whole.
Significant figures. No box mentions them. The only CED wording on the subject sits inside the task verb definition of Calculate, which asks for "correct labeling of units and significant figures".
Relativistic effects. No box mentions them, in any of the four courses.
Signs. No box fixes a positive direction, a sign convention for work, or a sign convention for heat. Those come from the equation sheet, which prints $\Delta U = Q + W$ with $W = -P\Delta V$ , meaning work done on the gas.
Massless pulleys or frictionless axles. Neither phrase appears in any of the four boxes. A question that wants them says so.

If a resource tells you the AP exam "assumes" something that is not one of the sixteen rows above, treat that as folklore until it is quoted from a printed page.

Using the conventions in a free-response answer

Two habits earn or lose points here.

The first is not restating them. A conventions box exists so that you do not have to write "assuming the string is ideal" before every tension answer. Time spent on that is time not spent on the justification that the rubric is actually paying for.

The second is noticing when a question has stated otherwise. The escape clause is the whole point of the box, and a question overrides a convention the moment it gives you the number that contradicts it. A coefficient of friction, a drag force law, a battery's internal resistance, a dielectric constant other than 1.0, a non-ohmic bulb described by a curve rather than a resistance: each of those is a question telling you the default is off. Students who have memorized the box and stopped reading are the ones who use the default anyway.

A third, quieter habit: the conventions are not a licence to skip a free-body diagram arrow. Negligible air resistance means the drag arrow is absent because it is zero, not because you decided not to draw it. Diagrams are graded against what the question actually contains.

What the monatomic convention is worth on AP Physics 2

A sealed rigid container holds 2.0 mol of an ideal gas at 300 K. Find the internal energy of the gas, and state how the answer would change if the gas were diatomic.

AP Physics 2 convention 5 reads "Ideal gases are monatomic", so no further information is needed to choose the model.
The AP Physics 2 equation sheet prints internal energy for that model as $U = \frac{3}{2}nRT$ , with the universal gas constant $R = 8.31 \text{ J/(mol}\cdot\text{K)}$ from the constants table.
Substitute: $U = \frac{3}{2}(2.0 \text{ mol})(8.31 \text{ J/(mol}\cdot\text{K)})(300 \text{ K})$ .
Work the product left to right: $(8.31)(300) = 2493$ , then $(2493)(2.0) = 4986$ , then $(1.5)(4986) = 7479 \text{ J}$ .
Round to the two significant figures the data carry: $U = 7.5 \times 10^3 \text{ J}$ .
For a diatomic gas the factor would be $5/2$ rather than $3/2$ , giving $12465 \text{ J}$ , or $1.2 \times 10^4 \text{ J}$ . That is $5/3$ of the monatomic value, so the convention is worth a factor of about 1.67 on this answer.

$U = 7.5 \times 10^3 \text{ J}$ . The convention is not decoration: a diatomic gas would give $1.2 \times 10^4 \text{ J}$ , and the AP Physics 2 sheet prints only the monatomic form.

Air-filled capacitors, and what the convention removes

A parallel plate capacitor has plates of area $0.020 \text{ m}^2$ separated by $1.0 \times 10^{-3} \text{ m}$ . Find its capacitance on an AP Physics 2 or AP Physics C: E&M exam where no dielectric is mentioned.

Both booklets print "Capacitors are air-filled" with dielectric constant $\kappa = 1.0$ , so the general sheet equation $C = \dfrac{\kappa \varepsilon_0 A}{d}$ collapses to $C = \dfrac{\varepsilon_0 A}{d}$ .
Take $\varepsilon_0 = 8.85 \times 10^{-12} \text{ C}^2/(\text{N}\cdot\text{m}^2)$ from the constants table.
Numerator: $(8.85 \times 10^{-12})(0.020) = 1.77 \times 10^{-13}$ .
Divide by the separation: $\dfrac{1.77 \times 10^{-13}}{1.0 \times 10^{-3}} = 1.77 \times 10^{-10} \text{ F}$ .
Round to two significant figures: $C = 1.8 \times 10^{-10} \text{ F}$ , which is 180 pF.
If the question had inserted a dielectric with $\kappa = 2.5$ , the convention would have been overridden and the answer would be $4.4 \times 10^{-10} \text{ F}$ .

$C = 1.8 \times 10^{-10} \text{ F}$ , about 180 pF. The convention is what lets you drop $\kappa$ without saying so.

Frequently asked questions

Does the AP Physics exam tell you to ignore air resistance?

Three of the four booklets do, in different words. AP Physics 1 and AP Physics C: Mechanics both print "Air resistance is assumed to be negligible unless otherwise stated." AP Physics C: Electricity and Magnetism prints "Frictional forces and air resistance are negligible." AP Physics 2 is the exception: its box prints "Frictional forces are negligible" and never names air resistance separately. In all four cases the assumption is off the moment a question gives you a drag law or a resistive force.

Are ideal gases monatomic on the AP Physics exam?

On AP Physics 2, yes. Its conventions box prints "Ideal gases are monatomic" as one of nine bullets, and the AP Physics 2 equation sheet follows through by printing internal energy only as three-halves nRT. None of the other three courses print that bullet, and none of them has a thermodynamics unit. So the statement is true of AP Physics 2 and says nothing at all about AP Physics 1 or either Physics C exam.

How many conventions does each AP Physics exam print?

AP Physics 1 prints four, AP Physics 2 prints nine, AP Physics C: Mechanics prints three, and AP Physics C: Electricity and Magnetism prints seven. Counting distinct bullet texts across all four booklets rather than per course gives sixteen, because several bullets are worded differently in different courses even when they carry the same idea. C: Mechanics prints the shortest box and its three bullets are word for word the first three of the AP Physics 1 box.

Is g equal to 9.8 one of the exam conventions?

No. The value of g is printed in the Constants and Conversion Factors table, one box above the conventions, as 9.8 metres per second squared and 9.8 newtons per kilogram. The conventions box never mentions it. This distinction matters because AP Physics 1 separately states that the exam will use about 10 wherever a numerical value for g is required, while also saying you are not penalised for correctly using 9.8 or 9.81. That is a boundary statement in the course framework, not a convention in the exam booklet.

What does unless otherwise stated actually let a question do?

It lets the question switch any default off by supplying information that contradicts it. A coefficient of friction, a numerical drag force, a battery's internal resistance, a dielectric constant other than 1.0, a bulb whose current-voltage graph curves: each of those is the question stating otherwise. You do not need a sentence saying the convention is suspended. The data are the statement. Using the default value anyway after a question has overridden it is one of the cheapest ways to lose a point.

Do the AP Physics C exams share a conventions box?

No, and they differ more than most people expect. C: Mechanics prints three bullets: inertial frame, negligible air resistance, ideal springs and strings. C: Electricity and Magnetism prints seven: inertial frame, negligible frictional forces and air resistance, ideal strings, springs, batteries, wires and meters, zero electric potential at infinite distance from an isolated point charge, current in the direction positive charges would drift, ohmic resistors and lightbulbs, and air-filled capacitors. Only the frame-of-reference idea and the ideal-object idea appear in both, and even those are worded differently.

Where can I read the conventions box myself?

In the Table of Information appendix at the back of each course and exam description, all of which are free from College Board. In the current editions, effective Fall 2024, the box appears on printed page 211 of the AP Physics 1 CED, page 218 of AP Physics 2, page 204 of AP Physics C: Mechanics, and page 178 of AP Physics C: Electricity and Magnetism. Each box sits below the trigonometric values table and above the equation lists.