14 . Magnetic force on a wire
15 . Electric force on a charge
16 . Electric potential energy
17 . Magnetic field around a long, straight, current-carrying wire
18 . Time constant for an RC circuit
19 . Resistance of a wire in terms of its dimensions
20 . Electric field due to a point charge
So, How Did You Do?
Grade yourself according to this scale.
You may think we’re joking about our grading system, but we’re completely serious. Knowing your
equations is absolutely imperative. Even if you missed one question on the quiz, you need to study your
equations. Right now! A student who is ready to take the AP exam is one who can ace an “equations quiz”
without even thinking about it. How ready are you?
Equations Are Crucial
It’s easy to make an argument against memorizing equations. For starters, you’re given all the equations
you need on the exam. And besides, you can miss a whole bunch of questions on the test and still get a 5.
But equations are the nuts and bolts of physics. They’re the fundamentals. They should be the
foundation on which your understanding of physics is built. Not knowing an equation—even one—shows
that your knowledge of physics is incomplete. And every question on the AP exam assumes complete
knowledge of physics.
Now you get equation sheets on the multiple choice section, too.
What About the Free-Response Section?
The free-response questions test your ability to solve complex, multistep problems. They also test your
understanding of equations. You need to figure out which equations to use when and how. The makers of
the test are being nice by giving you the equation sheet—they’re reminding you of all the equations you
already know in case you cannot think of that certain equation that you know would be just perfect to
solve a certain problem. But the sheet is intended to be nothing more than a reminder. It will not tell you
when to use an equation or which equation would be best in solving a particular problem. You have to
know that. And you will know that only if you have intimate knowledge of every equation.