How Your Knowledge Will Be Tested

How Your Knowledge Will Be Tested

There are three different levels on which your understanding of physics may be tested. While questions on kinematics often require that you make use of some of the formulas for kinematic motion, questions on quantum physics or atomic structure may often ask just that you remember the name of a particular concept. Knowing the different ways in which your knowledge may be tested should help you better prepare yourself for the exam.

Recall (20–33% of the test)

These are questions of the either-you-know-it-or-you-don’t variety. They test your understanding of the basic concepts of physics. No equations or calculations are necessary for these questions. They’re simply a matter of knowing your stuff.

Single-Concept Problem (40–53% of the test)

These questions expect you to recall, and make use of, one physical relationship, formula, or equation. This might involve plugging numbers into a kinematic equation of motion, or it might involve recalling the equation E = hf and solving for E or f. These questions test to see if you know important formulas and how to apply them.

Multiple-Concept Problem (20–33% of the test)

These questions expect you to bring together two or more different relationships, formulas, or equations. This could involve bringing together two formulas from the same subject—for instance, a problem in linear momentum that requires you to calculate the momentum of an object before a collision so that you can calculate its velocity after the collision—or it may bring together formulas from two different subjects—for instance, a problem that involves an electric point charge moving in circular motion in a magnetic field. These questions test not only your knowledge of physical relationships, but also your ability to integrate more than one in a complex problem.

You’re probably thinking that the recall questions are the easiest, and the multiple-concept problems are the hardest. This isn’t necessarily true. Most people have an easier time bringing together two simple principles of mechanics than recalling the significance of the Rutherford experiment. You’ll find all three types of questions throughout the test, and at different levels of difficulty. Ultimately, every question tests the very same thing: whether you’ve grasped the basic principles of physics.

Format of SAT II Physics

SAT II Physics is a one-hour-long test composed of 75 questions and divided into two parts. You can answer questions in any order you like, though you’re less likely to accidentally leave a question out if you answer them in the order in which they appear. Part A—classification questions—takes up the first 12 or 13 questions of the test, while Part B—five-choice completion questions—takes up the remaining 62 or 63 questions.

Part A: Classification Questions

Classification questions are the reverse of normal multiple-choice question: they give you the answers first and the questions second. You’ll be presented with five possible answer choices, and then a string of two to four questions to which those answer choices apply. The answer choices are usually either graphs or the names of five related laws or concepts. Because they allow for several questions on the same topic, classification questions will ask you to exhibit a fuller understanding of the topic at hand.

The level of difficulty within any set of questions is generally pretty random: you can’t expect the first question in a set to be easier than the last. However, each set of classification questions is generally a bit harder than the one that came before. You should expect questions 11–13 to be harder than questions 1–4.

Classification Question Example

Directions: Each set of lettered choices below refers to the numbered questions immediately following it. Select the one lettered choice that best answers each question and then blacken the corresponding space on the answer sheet. A choice may be used once, more than once, or not at all in each set. Questions 1–3 A boy throws a ball straight up in the air and then catches it again. 1. Which of the above graphs best represents the ball’s position with respect to time? 2. Which of the above graphs best represents the ball’s velocity with respect to time? 3. Which of the above graphs best represents the ball’s acceleration with respect to time?

Explanation

You can usually answer classification questions a bit more quickly than the standard five-choice completion questions, since you only need to review one set of answer choices to answer a series of questions.

The answer to question 1 is B. The ball’s position with respect to time can be expressed by the equation y = –¹/₂ gt², where g is the downward, acceleration due to gravity. As we can see, the graph of y against t is an upside-down parabola. In more intuitive terms, we know that, over time, a ball thrown in the air will rise, slow down, stop, and then descend.

The answer to question 2 is E. The acceleration due to gravity means that the velocity of the ball will decrease at a steady rate. On the downward half of the ball’s trajectory, the velocity will be negative, so E, and not A, is the correct graph.

The answer to question 3 is D. The acceleration due to gravity is constant throughout the ball’s trajectory, and since it is in a downward direction, its value is negative.

Don’t worry if the question confused you and the explanations didn’t help. This material and more will be covered in Chapter 2: Kinematics. This was just an exercise to show you how a classification question is formatted.

Part B: Five-Choice Completion Questions

These are the multiple-choice questions we all know and love, and the lifeblood of any multiple-choice exam. You know the drill: they ask a question, give you five possible answer choices, and you pick the best one. Got it? Good. An example appears below.

While you’ll often find two or three questions in a row that deal with the same topic in physics, there is no pattern. You might find a question on modern physics followed by a question on dynamics followed by a question on optics. However, there is a general tendency for the questions to become more difficult as you progress.

Five-Choice Completion Question Example

Directions: Each of the questions of incomplete statements below is followed by five suggested answers or completions. Select the one that is best in each case and then fill in the corresponding oval on the answer sheet. 1. A gas in a closed container is steadily heated over a period of time. Which of the following statements is true of this process? (A) The average kinetic energy of the gas molecules decreases (B) The mass of the container increases (C) The pressure exerted by the gas on the walls of the container increases (D) The gas changes phase into a liquid (E) The specific heat of the gas decreases

Explanation

The answer to this question is C. The key lies in remembering the ideal gas law: PV = nRT. According to this formula, an increase in temperature is accompanied by an increase in pressure. A is wrong, since the average kinetic energy of gas molecules corresponds to their temperature: if the temperature increases, so does the average kinetic energy of the molecules. B is wrong because we’re dealing with a closed container: the mass cannot either increase or decrease. D is wrong because a gas must be cooled, not heated, to change phase into a liquid. Finally, E is wrong because the specific heat of any substance is a constant, and not subject to change. We’ll touch on all this and more in Chapter 9: Thermal Physics.

Introduction to SAT II Physics

The best way to do well on SAT II Physics is to be really good at physics. For that, there is no substitute. But the physics whiz who spends the week before SAT II Physics cramming on Lagrangian mechanics and Dirac notation probably won’t fare any better than the average student who reviews this book carefully. Why? Because SAT II Physics Tests (and first-year university courses) do not cover Lagrangian mechanics or Dirac notation. Take this moment to sigh with relief.

This chapter will tell you precisely what SAT II Physics will test you on, how the test breaks down, and what format the questions will take. You should read this information carefully and base your study plan around it. There’s no use spending hours on end studying for stuff that’s not relevant to the test. Knowing nothing about electromagnetic induction will hurt you on the test, but nowhere near as much as knowing nothing about optics will.

Content of SAT II Physics

Math and physics go hand in hand, right? You might be surprised, then, to learn that you aren’t allowed to use a calculator on SAT II Physics. The math required of you never goes beyond simple arithmetic and manipulation of equations. You have, on average, 48 seconds to answer each question, and the people at ETS realize that isn’t enough time to delve into problems involving simultaneous equations or complex trigonometry. They’re more interested in testing your grasp of the basic concepts of physics. If you’ve grasped these concepts, your weakness in math isn’t going to hurt you.

ETS breaks down the concepts you need to know for the test into six categories:

Topic	Percentage of the Test
Mechanics	34–38%
Electricity and Magnetism	22–26%
Waves	15–19%
Heat, Kinetic Theory, and Thermodynamics	8–12%
Modern Physics	8–12%
Miscellaneous	2–4%

While these categories are helpful, they are also very broad. You may be a whiz with waves but a loser with lenses, and want to know how much of the waves portion of the test will be devoted to optics. To help you out, we’ve broken the test down even further so that you’ll know exactly where to expect to feel the squeeze. (These figures are only approximations, and may vary from test to test.)

Topic	% of the Test	Number of Questions
Mechanics	34–38%	25–29
Vectors	2%	1–2
Kinematics	6%	4–5
Dynamics	10%	7–8
Work, Energy, and Power	6%	4–5
Special Problems in Mechanics	5%	3–4
Linear Momentum	2%	1–2
Rotational Motion	1%	0–1
Circular Motion and Gravitation	4%	2–4
Thermal Physics	8–12%	6–10
Heat and Temperature	4%	2–4
Kinetic Theory and Ideal Gas Laws	2–3%	1–2
Laws of Thermodynamics	1%	0–2
Heat Engines	2–3%	1–2
Electricity & Magnetism	22–26%	16–20
Electric Fields, Forces, Potential	10%	7–8
Magnetic Fields and Forces	6%	4–5
Electromagnetic Induction	1%	1
Circuits and Circuit Elements	6%	4–5
Waves	15–19%	11–15
Waves	10%	7–8
Optics	7%	5–6
Modern Physics	8–12%	6–9
Special Relativity	1–2%	1–2
Atomic Models	3%	2–3
Quantum Physics	2%	1–2
Nuclear Physics	3%	2–3
Miscellaneous	2–4%	1–3
Graph Analysis	1–2%	0–2
Equation Manipulation	0.5–1%	0–1
Significant Digits and Lab Skills	0.5–1%	0–1

The chapters of this book are organized according to these categories. If a physics topic is not in this book, you don’t need to know it. Here’s some other helpful information:

You need to know: the formulas expressing physical relationships (such as F = ma), how to manipulate equations, how to read a graph

You don’t need to know: trig identities, calculus, three-dimensional vectors and graphs, physical constants (such as G = 6.6710^–11 N·m² ⁄ kg²)