## 5 Steps to a 5: AP Physics 1: Algebra-Based 2017 (2016)

### STEP __1__

### Get to Know the Exam and Set Up Your Study Program

### CHAPTER 2

### Understanding the Exam: The AP Physics 1 Revolution

**IN THIS CHAPTER**

**Summary:** The AP Physics 1, Algebra-Based Exam requires less calculation and more written explanations of physics than any previous standardized physics exam. This chapter provides a deeper analysis of the AP Physics 1, Algebra-Based Exam, explaining what the test is like and how it is different from traditional physics tests.

**Key Ideas**

The AP Physics 1, Algebra-Based Exam is less focused on getting the “right” numerical answer to a problem and more focused on explaining and applying the concepts of physics.

The AP Physics 1, Algebra-Based Exam is no walk in the park. Although it covers fewer topics, has fewer questions, and contains less math than the old AP Physics B Exam, it requires a deeper understanding of physics. The AP Physics 1 exam is more difficult than a typical high school honors physics exam.

**What Happened to the AP Physics Test?**

The AP Physics 1, Algebra-Based Exam is not like anything your father or even your older sister took. The AP Physics 1, Algebra-Based curriculum has undergone a radical transformation that has eliminated the advanced mathematics but added a profound understanding of the science of physics.

**A Little History**

In the 1970s and 1980s, a typical physics professor gave lectures heavily focused on mathematics to first-year students and then administered exams that demanded clever algebraic manipulation. The AP Physics B exams of that era reflected the mathematical nature of college physics.

In the 1990s, a new generation of physics professors promoted a different kind of physics teaching that was just as rigorous but that demanded more explanations and less algebraic skill. The meaning of the math became more important than the math itself. AP exams began to include more questions asking for descriptions of experimental techniques, for justification of numerical answers, and for explanations in words.

When the College Board received a grant to redesign their science courses in the early 2000s, the curriculum design committee decided to move even farther away from calculation and more toward verbal explanation. They minimized the number of topics on the newest AP physics exams, and they decreased the number of questions on the exams. That way, they reasoned, the exam could demand more writing and more detailed explanations in the responses.

**Goal of the AP Physics 1 Revolution: The Best College Physics Course, Not Just the “Typical” College Physics Course**

The fundamental purpose of the College Board”s AP program has always been to give advanced high school students access to college-level coursework. Historically, the goal was to create exams that mimic the content and level of the typical, average courses at an American university.

However, in redesigning their science courses, the development committees aimed higher—the stated goal now is for the AP exams to reflect best practices as well as the content and difficulty level of only the best college courses. In general, the “best” college classes include lots of demonstrations, laboratory work, and descriptive as well as calculational physics.

**What Is AP Physics 1? Eleven Things You Should Know About the Course and Exam**

You”ll do better on a test if you understand the test and what”s being tested. In this section you”ll learn key facts about the AP Physics 1 Exam—facts that will help you know what to expect and, as a result, better prepare for the test.

**AP Physics 1 Is Not a Broad Course**

Whereas the old AP Physics B course included between five and eight major topic areas, AP Physics 1 is limited to just three:

- Mechanics
- Electricity
- Waves

Of these, mechanics will dominate the exam. Subtopics of mechanics primarily include motion, force, momentum, energy, and rotation. The study of electricity is limited to circuits and the force between charged particles. As an approximation, AP Physics 1 contains only a bit more than half as much material as the old AP Physics B course did. And that makes sense—AP Physics 1 is designed to replicate the first semester of an algebra-based freshman college course. AP Physics 2 covers the second-semester material.

**AP Physics 1 Is Designed to Be a First-Time Introduction to Physics**

The current AP Physics C exams, and the old AP Physics B Exam, were developed with the understanding that students would already have taken a high-school-level introduction to physics. But many high school students want to, and are ready to, dive right into algebra-based physics at the college level. AP Physics 1 has been written to set up these students for success. Thus, there is a reduction in the amount of material covered. Even if you”ve never seen physics before, you will have the time in AP Physics 1 to develop both your content knowledge and your physics reasoning skills enough to perform well on the exam.

**AP Physics 1 Is Not a Math Course**

There are only three high-school-level mathematical skills you need in order to understand AP Physics 1 material:

- You must have thorough facility with algebraic equations in a single variable.
- You must be able to calculate, and to understand the meaning of, the slope and area of a graph.
^{1} - You must be able to use the definitions of the basic trig functions sine, cosine, and tangent.
^{2}

That”s it. You covered these things in your Algebra 1 and geometry courses. You don”t need matrices, factoring of polynomials, the quadratic formula, trigonometric identities, conic sections, or whatever else you are studying in Algebra II or precalculus.

**AP Physics 1 Is Not About Numbers**

Yes, you must use numbers occasionally. Yet you must understand that the number you get in answer to a question is always subordinate to what that number represents.

Many misconceptions about physics start in math class. There, your teacher shows you how to do a type of problem, and then you do several variations of that same problem for homework. The answer to one of these problems might be 30,000,000, and another 16.5. It doesn”t matter … in fact, the book (or your teacher) probably made up random numbers to go into the problem to begin with. The “problem” consists of manipulating these random numbers a certain way to get a certain answer.

In physics, though, *every number has meaning* . Your answer will not be 30,000,000; the answer may be 30,000,000 joules, or 30,000,000 seconds, but not just 30,000,000. If you don”t see the difference, you”re missing the fundamental point of physics.

We use numbers to represent *real* goings-on in nature. The amount 30,000,000 joules (or 30 megajoules) is an energy; it could be the kinetic energy of an antitank weapon or the gravitational energy of an aircraft carrier raised up a foot or so.^{ }^{3}^{ }Thirty million seconds is a time, not a few hours or a few centuries, but about one year. These two “30,000,000” responses mean entirely different things. If you simply give a number as an answer, you”re doing a math problem. It is only when you can explain the meaning of a result that you may truly claim to understand physics.

**AP Physics 1 Requires Quantitative and Semiquantitative Reasoning**

You”ll only occasionally be asked to make numerical calculations. But you”ll often be required to use mathematical *reasoning* .

“Quantitative” reasoning means not only performing direct calculations, but also explaining why those calculations come out the way they do. You”ll be asked to explain whether quantities increase or decrease just by looking at the relevant equation, and without necessarily performing the calculations. You”ll need to recognize that a problem is solvable when one equation with a single variable can be written, or when two equations with two variables can be written, or even when three equations with three variables can be written. You”ll not be asked to solve even mildly complicated multivariable problems, but you must recognize when and explain why they are or aren”t solvable.

“Semiquantitative” reasoning involves anticipating how the structure of an equation will affect the result of a calculation, even when no values in the equation are known. Increasing a variable in the numerator of an equation increases the quantity being calculated; increasing a variable in the denominator decreases the quantity being calculated. Doubling a term in the numerator also doubles the entire quantity, except if that term is squared (in which case the quantity is quadrupled) or square-rooted (in which case the quantity is multiplied by 1.4).

For example, the question “Calculate the acceleration of the 250-g cart” will be legitimate on the AP Physics 1 Exam. But more often the question will be rephrased to get at the heart of your ability to reason about physics, not just at your math skills. For example:

- Rank the accelerations of these carts from greatest to least; justify your ranking.
- Can the acceleration of the 250-g cart be calculated from the given information? If not, what other information is required?
- Explain how you would use a graph to determine the acceleration of the 250-g cart.
- How would the acceleration of a 500-g cart compare to the acceleration of the 250-g cart?
- Is the acceleration of the cart greater than, less than, or equal to
*g*?

**AP Physics 1 Requires Familiarity with Lab Work**

Every physics problem that asks for calculation, quantitative reasoning, or semiquantitative reasoning is, in truth, asking for an experimental prediction.

When doing calculations, what differentiates physics from math class? In physics, every calculation can, in principle, be verified by an experimental measurement. Merely using an equation to calculate that a cart”s acceleration is 2.8 m/s per second is a math problem, one that you might see in an Algebra 1 class. It”s only a physics problem because you can, in fact, go to a cabinet and pull out a 250-g cart and a motion detector that will measure the cart”s acceleration. If you set up the situation that was described in the problem, you”d better get an acceleration of 2.8 m/s per second; otherwise, either the calculational approach was incorrect (e.g., the equation you used might not apply to this situation), or the experiment was set up inappropriately (e.g., the problem assumed a level surface, but your track was slanted).

What”s particularly nice about AP Physics 1 is that almost every problem posed in this course can be set up for experimental measurement within the realm of most students” experience. Carts can be set up to collide in your classroom. It”s straightforward to take smartphone video of cars on a freeway or of a roller coaster. Computerized data collection—generally using equipment from PASCO or Vernier—should be part of your classroom experience, so that you”re familiar with using force probes, motion detectors, photogates, and so on.^{ }^{4}

Any physical situation can spawn a laboratory-based experimental question. Be prepared to describe experiments and to analyze data produced by experiments:

- Describe an experiment which uses commonly available laboratory equipment to measure the acceleration of the 250 g cart.
- In the laboratory, this table of the cart”s speed as a function of time was produced. Use the data to determine the car”s acceleration.
- The acceleration of the cart is calculated to be 2.8 m/s per second, but in the laboratory, a student measures the cart to have an acceleration of 4.1 m/s per second. Which of the following might explain the discrepancy between theory and experiment?

**AP Physics 1 Does Not Require That You Perform a Specific Set of Programmed Laboratory Exercises**

In AP Biology, students are expected to be familiar with, and to have actually done, a set of experiments. Biology exam questions will refer to these common experiments, expecting prior knowledge to carry students. This approach is completely different from that in AP Physics.

AP Physics certainly requires experimental skills, as described above. Teachers are required by the Course Audit to spend at least 25 percent of class time doing live, hands-on laboratory exercises. Yet, the actual nature of those exercises is left to the teacher. Since virtually every possible AP Physics 1 question can be set up as an experiment, there are limitless possibilities for lab work. Creativity in lab work is prized on the AP Physics exam.

It”s critical that you don”t think of the “lab” as a place where you follow the steps in a procedure to produce a canned result that matches your teacher”s expectation. Rather, think of the lab as a place to play, a place to re-create the calculational problems you”ve been solving in class. Lab is a place where you test the equations and concepts to see if they work.

That”s silly. Of course these equations and concepts work. Do you really expect me, a high school student, to disprove the conservation of momentum in a collision? Really!

Yeah, no one expects you to win a Nobel Prize in your AP Physics 1 laboratory. What is expected is that you go beyond stating “facts” of physics as gospel. A physicist always asks, “What”s the evidence?” “How do we know that?” The AP Exam expects you to be able to use conservation of momentum to calculate the speed of a cart after collision, sure; but it also expects you to explain why conservation of momentum is valid in this situation and, this is important, to explain *what evidence exists that conservation of momentum is a valid principle in the first place* .

The “evidence” for each physics fact comes from an experiment. You should be able to articulate how an experiment could be designed to test the validity of any fact; you should be able to use equipment creatively to make a measurement of any quantity that might show up in a calculational problem.

**AP Physics 1 Requires Writing**

The free-response questions on the AP Physics 1 Exam will be more similar to those on the AP Biology or AP Economics exams than to those on AP Calculus or AP Physics C exams. Do not expect to answer exclusively in mathematical symbols and numbers. Whereas AP Physics B questions rarely required more than a couple of sentences at a time, the new exam will ask for short answers, descriptions, and explanations “without equations or calculations.”

This doesn”t mean you need to develop your storytelling skills. The writing required is always straightforward and to the point. A perfect response on the AP Physics 1 Exam might draw all sorts of complaints from your English teacher. While you need to use (reasonably) grammatically correct sentences, your language and vocabulary should be simple, not flowery. Your sentence structure doesn”t need to be varied and interesting. You don”t need to grab your reader”s attention or to segue appropriately between paragraphs and ideas.

Just write, without worrying about how your writing sounds to a professional. Imagine that the person reading your writing is a student at the same level of physics as you. Don”t explain your answers the way you think a college professor would; explain your answers the way you wish your teacher would explain them—simply and clearly, but completely. Practice this sort of writing on your problem sets.

**AP Physics 1 Requires “Multiple Representations” of Physics Concepts**

This means you should be comfortable explaining physics with words, equations, diagrams, and numbers. When you solve problems in your physics class, practice using these elements in every solution—even if your teacher doesn”t explicitly require them. In my own class, if a student doesn”t use at least three of these four elements in response to a homework question, the student usually loses significant credit.

Don”t be shy about drawing diagrams. Try doing your homework on graph paper or unlined paper, rather than on standard notebook paper. Think of the paper as a blank canvas that needs to be filled in with your understanding of the solution to a problem. Lined notebook paper is far too restricting. It implies that you should be writing rows of words, with maybe an equation.^{ }^{5}^{ }Words can be written on a diagram, possibly with arrows to point out the important parts. Graphs and pictures can be drawn anywhere. Equations don”t have to be placed one after the other in columns. A series of equations, however you present them, should always include some words describing the purpose of the equations in the problem”s solution.

Then on the exam, you”ll be well practiced in interpreting every possible representation of a physics explanation. Don”t worry, you”ll be asked for such interpretations on the multiple-choice section, and you”ll be asked to use multiple representations of concepts on the free-response questions.

**The AP Physics 1 Exam Is Designed to Give You the Time You Need to Answer the Questions Posed**

As the new exams were in the development process, it became clear that the heightened demands for writing, for experimental interpretation and description, and for multiple representations of physics concepts would require a lot of time and thought. The committees in charge of creating AP Physics 1 were in agreement that students must be given the time necessary to respond in a complete way.

Even students with strong physics abilities are often pressed for time on the AP Physics C or the old AP Physics B exams. The rule of thumb there was to spend about one minute per point: one minute on a multiple-choice question, 15 minutes on a 15-point free-response question, and so on. Therefore, students were advised to work quickly, eschewing in-depth thought for quick solution methods.

But AP Physics 1 is about half as long. The rule of thumb will be to spend in the neighborhood of *two* minutes per point. You”ll get 50 multiple-choice questions to be completed in 90 minutes. Knock a few off quickly, and you can really think carefully about some while easily maintaining a just-under-two-minute-per-problem pace. The free-response section will have two long 12-point questions and three short 7-point questions and also will be 90 minutes in length. Yeah, you”ll need to work steadily without dawdling, otherwise you might run out of time even on this exam. But you”ll have time to think before you write; then you”ll have time to write everything you need to communicate your answer.

Practice this new sort of time management on your homework for physics class. Instead of doing a zillion homework problems as quickly as you can, try picking one or two for a full-on, long-form treatment. Answer using multiple representations. Explain the answer, how you got it, how it would change if the problem inputs changed, and why you used the fundamental approach you used. Make the solution so complete that it could serve as the basis for a set of PowerPoint slides that could present your solution to a classmate. And do it all in less than 30 minutes. When you can do that, you”re ready for the AP Physics 1 Exam.

**AP Physics 1 Is a Difficult, High-Level College Course**

Some may get the impression that because calculation is minimized and so few topics are covered, this course will be a “piece of cake.” Wrong. My own impression, and the impression of all experts who have looked carefully at the types of questions asked on the new exam, is that AP Physics 1 is substantially more difficult than AP Physics B used to be.

People have the false impression that “lots of writing” means “easy to get some credit, because I can use lots of big words full of sound and fury.” You will find that the AP readers are as adept at recognizing baloney as they are at recognizing good physics. You will be less likely to find points awarded for attempting to use a correct equation. While partial credit on the free response will still be copiously available, that credit will generally require a good, if incomplete, understanding of physics, and will not be attainable via guesswork.

Expect wailing and gnashing of teeth again when scores come out after the exam, because too many teachers and students are still thinking of physics as plugging numbers into equations. But you won”t wail, of course, because you”ve read this book; you know what to expect; and you know that a true understanding of physics requires that you be able to solve problems, explain how you solved them, explain what concepts you used to solve them, explain why those concepts apply, and explain how you could experimentally demonstrate your solution. Meanwhile, those with gnashed teeth remain stuck with the idea that just producing an answer is enough.

__ ^{1}__ Note that the calculus extensions of these concepts as “derivatives” and “integrals” are utterly irrelevant to and useless in AP Physics 1.

__ ^{2}__ This knowledge is often expressed as “SOHCAHTOA”: In a right triangle, the

**S**ine is

**O**pposite over

**H**ypotenuse. …

__ ^{3}__ Interestingly, when you use this much electrical energy in your house, it would cost you in the neighborhood of $1.

__ ^{4}__ If your classroom does

*not*have at least one set of PASCO or Vernier probes, your school probably doesn”t meet the requirements of the AP Course Audit. Access to some of the same type of laboratory equipment that is available in most colleges is a prerequisite for the College Board, allowing a school to label its course as “AP.” See the “AP Central” portion of the College Board”s official website for details about the course audit.

__ ^{5}__ And that equation”s fraction bar, if there is one, screws up the look of the words.