AP® Physics 1 Crash Course Book + Online: Get a Higher Score in Less Time

PART I

INTRODUCTION

Chapter 1

Keys for Success on the AP Physics 1 Exam

Congratulations on your decision to take AP Physics 1. Taking an AP course, especially an AP science course, is a challenging endeavor. AP courses represent college-level classes that you take in high school, so they are supposed to be challenging. But with your hard work, the help of your teacher, and this test prep, you will be guided toward success on this exam and in college.

The information presented in this book is meant to prepare you for the AP Physics 1 exam, based on information currently available from the College Board. The exam will test your critical-thinking skills, your ability to explain and reason both qualitatively and quantitatively, and your ability to show that you have an enduring understanding of physics that will support future coursework in science.

Let’s take a look at the exam!

1.The Structure of the Exam

The AP Physics 1 exam consists of both multiple-choice and free-response questions.

Section I—Multiple Choice—90 Minutes

•45 multiple-choice questions with only one correct answer

•5 multiple-choice questions with two correct answers (you must choose both correct answers to get credit for the question)

Section II—Free-Response Questions—90 Minutes

There are 5 free-response questions on this section of the exam. These include:

•1 experimental design question

•1 quantitative/qualitative translation

•3 short-answer questions

Each of the two sections of the exam is worth 50 percent of your score. The multiple-choice section is scored electronically and you are not penalized for guessing.

2.The AP Physics 1 Outline

The AP Physics 1 Curriculum Framework published by the College Board does not specifically state the units or topics that will be taught in a typical AP Physics 1 course. The Framework is instead organized around seven Big Ideas that will reoccur as themes.

The College Board is no longer publishing a topical breakdown for the AP Physics 1 exam, nor is it providing percentages of the exam that relate to each topic. We do, however, know that the following seven topics will be on the AP Physics 1 exam:

Kinematics

Forces, Circular Motion and Gravity

Work and Energy

Impulse and Momentum

Rotation, Torque, and Angular Momentum

Mechanical Waves, Sound, and Simple Harmonic Motion

Electrostatics and Circuits

AP Physics 1 will require less calculation and more written explanation than its predecessor, the AP Physics B exam. In fact, it will require far more explanation than any other standardized physics exam. There will be fewer topics and less math, but it will require you to have a deeper conceptual understanding of the physics topics. AP Physics 1 is not about getting the right number, but about knowing (and being able to explain) what the numbers mean. You have to remember that in physics class, every number has a real meaning and represents real phenomena!

3.Types of questions on the exam

The AP Physics 1 exam contains several types of questions:

a.Descriptive problems

A descriptive problem is similar to what you’ve seen in your AP Physics 1 class and in your textbook. A descriptive problem sets up a situation and then asks you to conceptually discuss the situation.

Example:

A lightbulb is connected to a battery. A second identical lightbulb is connected in series with the first. Which of the following happens to the current and the resistance in the circuit?

(A)Both increase

(B)Both decrease

(C)The current increases since the resistance decreases.

(D)The current decreases since resistance increases.

b.Calculation problems

Calculation problems should be familiar to you from your class and textbook. These are straightforward calculations based on your knowledge of the situation and the equations.

Example:

A 5 kg box is pulled vertically at a constant speed of 5m/s. If the box is pulled for 3 seconds, the power developed during this time is

(A)25 watts

(B)75 watts

(C)83 watts

(D)250 watts

c.Ranking tasks

Ranking tasks present you with several pictures of similar objects or situations, and you are asked to rank them based on some unknown quantity.

Example:

Three softballs are thrown at different angles and at different speeds as shown below. Rank the balls on the basis of their acceleration at the top of their trajectory.

(A)1 > 2 > 3

(B)3 > 2 > 1

(C)1 = 2 = 3

(D)Accelerations are all zero at the top of the trajectory.

d.Semi-quantitative reasoning

Semi-quantitative reasoning questions ask you to solve problems that involve some algebra using only symbols. In a semi-quantitative reasoning problem, you might be asked to figure out how much further a car would skid before coming to a stop if it were going twice as fast on the same road. You’ll have to do some algebra to figure out what the relationship is between the initial velocity of the car and the skid distance for the car, and then see how increasing the initial velocity by a factor of two changes the skid distance. If you struggle with this kind of question, keep practicing! (It is okay to plug in numbers to test if you get stuck!)

Example:

A box of mass m slides off the edge of a horizontal table at speed v and lands a distance d from the edge of the table. A second identical box leaves the table at 3v and lands at:

(A)d

(B)

(C)3d

(D)9d

e.Experimental design

Experimental design questions set up a situation where an experimental procedure is needed to find a result. The answer choices will provide different ways to set up the required experiment. You must choose the experimental procedure that will get you the desired result. The best way to practice this kind of question is to get your hands on equipment and do lots of lab experiments yourself. By doing so, you’ll have an intuitive idea as to what will work and what won’t work.

Example:

An object of mass m is attached to a string of length l and is pulled back so that it is a height h above the lowest point. It is desired to determine what the speed v at the lowest point will be if the object is instead released from 2h. Which of the following procedures would accomplish that determination?

(A)Position a motion detector so that it will catch the entire motion of the object. On the velocity vs. time graph output by the detector, look at the maximum vertical axis value which shows the highest speed attained by the object.

(B)Place a photogate where the object will pass through it at the lowest point. Measure the time for the object to pass through the photogate. Divide the distance the object swings by that time.

(C)Position a motion detector under the lowest position of the object. Divide the distance traveled by the object by the time recorded by the motion detector.

(D)Place a motion detector under the lowest position of the object. Find the area under the curve of the position vs. time output by the detector.

f.Experimental analysis

Experimental analysis questions ask you to decide the best way to present the results of an experiment. You will often be given a data set and asked to analyze, or find a way to graph the given quantities, to find a given result.

Example:

Students conduct an experiment to calculate the acceleration due to gravity using a pendulum. The length of the pendulum is varied and the period of oscillation is measured. Which of the following will produce a slope that can help the students find g?

(A)T vs ℓ

(B)T² vs. ℓ

(C)T vs. ℓ²

(D)

g.Multiple-correct questions

Multiple-correct questions are new to the AP Physics 1 exam and will be the last 5 questions on the multiple-choice section (Questions 46-50). For a multiple-correct question, two of the four answers will be correct and you will have to identify both correct answers to get credit for the question. There will not be partial credit given on this section.

Example:

Which of the following two adjustments would increase the resistance of a long wire?

(A)Decrease the cross sectional area

(B)Increase the length of the wire

(C)Increase the voltage across the resistor

(D)Decrease the current across the resistor

4.Basic Test-Taking Strategies

The best way to prepare for the AP Physics 1 exam is to pay attention and work hard in your AP Physics class at school. Take full advantage of your time in class and at home during the year.

To prepare for the exam, use this book and take REA’s online practice exam. The practice exam will help you become comfortable with the format of the test and the types of questions that will be asked. If you need more practice tests, you can check the College Board website (www.collegeboard.org) for their released sample questions. The more you practice, the better you will do!

Read all the test questions carefully. There is a lot more reading on this exam than on other standardized exams. Take your time and focus on the question. The College Board knows that these questions take more time to read and answer, and they have given you that time, so don’t rush!

Although you can use a calculator on both sections of the exam, you shouldn’t need to use it more than a few times throughout the entire exam. Even on questions where calculation is required, you’ll often be asked to make an estimate, or the numbers will be simple enough for you to solve the problem in your head. So, start weaning yourself from your calculator now. Practice using diagrams and graphs. Practice writing the equation and deciding what you could solve for without actually solving, and use your calculator only as a last resort!

You will also have a table of information and an equation sheet that you may use on both the free-response and multiple-choice sections. But, just like your calculator, you shouldn’t need to use the equation sheet more than a few times. Now that calculation is a far less significant portion of the AP Physics 1 exam, the equation sheet will rarely be useful. If you do use it, use it carefully and wisely! Don’t go fishing for an equation to use. (You may end up looking for an equation for power and find p=mv, where the p means momentum, not power.)

There is no penalty for guessing on the exam, so don’t leave any question blank. Eliminate answer choices you know are wrong and then make your best guess. If you have time, go back and look over the questions that were difficult for you.

AP Physics 1 is not a broad course. It covers three basic topics: mechanics, electricity, and waves. The majority of the exam will be focused on mechanics. Keep in mind that AP Physics 1 is not a math course. You will have to solve equations with a single variable, calculate and understand the meaning of the slope and area under a graph, use the basic trigonometry functions of sine, cosine and tangent, and solve problems. But you also need to explain: how you solved the problem, what concepts you used, and why those concepts can be applied. (You can practice this all year as you work with the questions your teacher assigns. When you finish with a numerical answer, try writing a why paragraph.) Any numerical question in physics can be tested in the laboratory, and you must be able to articulate how this would be done.

5.What Should I Bring to the Exam?

1.Pencils and extra erasers

2.Black or blue pens for the free-response section

3.Calculator

4.Ruler

5.A noiseless watch

6.Your school code

7.A valid photo identification and your Social Security Number

And, although you’ve heard it before, here’s some last-minute advice: go to bed early the night before the exam and don’t study all night—it won’t do any good!

Good luck on your AP Physics 1 exam!

Solutions to Example Questions

a.(D) Adding a second bulb in series will increase the resistance of the circuit. Since there is only one loop for the current to travel, an increased resistance means a decreased current.

b.(D) Power can be calculated by P = Fv or . Either way you get the same answer. The force exerted to lift the 5 kg object at a constant speed must be equal to the object’s weight, or approximately 50 N. When pulled at a constant speed of 3 m/s, the power is P = (50 N)(5 m/s) = 250 Watts. During the 3 seconds, since the object is traveling at 5 m/s, the object’s displacement is 15 m. Therefore, the work done on the box is W = (Force)(Displacement) = (50 N)(15m) = 750 Nm; which makes the power equal to .

c.(C) The acceleration of an object in free fall is always 9.8 m/s/s. It doesn’t matter where in the trajectory the ball is or how fast, or at what angle, it was thrown. The acceleration is g, all day, every day.

d.(C) The time that the box will take to land depends only on the height of the table, which does not change. So the only thing that will affect the distance that the box travels before it lands is the speed with which it leaves the table. Since it is going three times as fast as the first box, it will land three times further from the edge of the table.

e.(A) We are looking for the max speed which can be read right off the velocity vs. time graph. Choice (B) would work if you used the width of the block instead of the distance the block swings. (C) a motion detector doesn’t give a time reading, and (D) the area under the position vs. time graph is not velocity.

f.(B) The equation for period of a simple pendulum is . A linear graph can be obtained if the students graph T² and ℓ. The slope of their graph would be .

g.(A) and (B) are correct. The equation for the resistance of a resistor is . You could increase the resistance of a resistor either by increasing the length of the resistor, decreasing the cross-sectional area or both. Be