FAQ for Physics 101

Q:What is Physics 101?

A: Physics 101 is the first semester of Pierce College's calculus-based introductory physics sequence. It covers mechanics (including measurement, motion, forces, energy, momentum, rotation, statics, gravity, oscillations, and fluids). (The second semester, Physics 102, covers electricity, magnetism, and thermodynamics, while the final semester, Physics 103, covers waves, optics, and modern physics.) The class includes both lecture and lab.
Physics 101 is primarily aimed at physics and engineering majors; math and computer science majors often take it as well, because it involves applications of those fields. The class is also useful for those majoring in other scientific fields, such as chemistry and biology. Physics 101 is open to anyone who is mathematically prepared and interested in the subject, including high-school students looking for something beyond their own school's offerings.

In the calculus-based physics sequence at Pierce, we use a number of materials and methods developed through physics education research, which have been shown to improve students' conceptual understanding and problem-solving skills. Basically, the idea is that you will learn much more by being actively involved, rather than just listening to the professor talk. Sure, I will lecture sometimes, but there will be many labs, interactive demonstrations, tutorials, and questions to be answered with clickers (remote-control devices that will allow you to vote electronically). And during the majority of class time, you will be working with your fellow students on problems, tutorials, or labs.

Q: I notice that the lecture and lab portions of the class are listed separately. Is it possible for me to take just the lecture without the lab, or vice versa?

A: No. Regulations require us to divide the class hours into lecture and lab when listing the course in the catalog, but the division is never so clean and strict in practice; any part of the class period may end up being used for lecture, lab, tutorial, or another group activity like problem-solving. The labs are fully integrated into the course and relate directly to the lectures; all students need to participate in both.

Q: When does Physics 101 meet for spring 2009?

A: The day section of Physics 101 meets on Tuesdays and Thursdays from 12:45 to 5:20 pm. (Note that class will be held for the full 4 hours and 35 minutes each day, regardless of whether a lab is scheduled that day. The divisions of time into "lecture" and "lab" in the published schedule of classes don't really mean anything in terms of the day-to-day planning of the course. Each class meeting will include 30 minutes of break time. There is also an evening section of P101 on Mondays and Wednesdays from 5:30-10:05 pm, which will be taught by Dr. Loveridge.) The first day of class will be Tuesday, February 10; the final exam will be given on Thursday, June 4.

Q: I'm a pre-med student. Should I be taking Physics 101?

A: Most medical schools now require a year of calculus-based laboratory physics. Physics 101 plus 102 does satisfy this requirement. If you're a pre-med student with strong math skills and a particular interest in physics, Physics 101 would be a good choice for you. However, there is an alternative that you should be aware of:

The Physics 66/67 (Physics for Life Science Majors) sequence at Pierce College is specifically designed for pre-med students and others interested in the biological sciences. This sequence of courses is calculus-based, but shorter and less mathematically demanding than the Physics 101/102/103 sequence. Physics 66 and 67 also put a special emphasis on biomedical applications of physics. So if you are pre-med, be sure you've considered both options and chosen the one that you prefer. Midway through each semester, a few students belatedly discover that they're in the "wrong" physics course; don't let this happen to you!

Q: When are the last possible dates to add and drop the class for the spring 2009 semester?

A: Last day to add: February 20, 2009

Note that this date is the last day to turn in the official paperwork for adding, for students who have already been attending the class and doing the work. Students who do not attend or contact the professor during the first week of class will not be allowed to add later.

Last day to drop with a refund: February 24, 2009

Last day to drop without a "W" grade: March 8, 2009

Last day to drop with a "W" grade: May 10, 2009

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Q: What are the prerequisites for Physics 101? Can I still take the class if I don't have them?

A: In order to enroll in Physics 101, students are required to have passed calculus 1 (Pierce's Math 261, high school calculus AB, or the equivalent), and be at least concurrently enrolled in calculus 2 (Pierce's Math 262, or the equivalent). Competence in algebra, trigonometry, and geometry is also presumed.

There is no official English prerequisite; however, the class will require a good deal of reading and writing. Some students who are learning English as a second language have done very well in Physics 101, but others have struggled severely because of the language barrier. Physics is not just a matter of solving equations; if you are not able to understand, or write, explanations of fairly complex and subtle concepts, you will not be able to do well in this class. If your English is not fluent, you may be better off taking physics in a later term after spending additional time improving your language skills.

If you have the proper math background, but are not able to enroll because of a simple bureaucratic problem, I will be happy to help you out. For example, if you took calculus long ago and don't have a transcript available, the system may not let you register. If something like this happens, please email me and explain your situation, and I will provide you with the paperwork so that you may enroll.

If you do not have the proper math background, I would strongly discourage you from taking the class. The prerequisite is there for a reason; math is an important tool for understanding and applying physics at this level. Working with derivatives and integrals will be a fundamental part of the course. If you come in without the required math skills, you're likely to spend the term confused and frustrated, and end up either dropping or receiving a poor grade. If you feel your situation is exceptional for some reason, you may email me and explain why you feel you should be admitted. I will read and consider all requests, but I make no promises to grant them.

Q: I tried to preregister for Physics 101 but found that the class was full. Is there anything I can do to get in?

A: Possibly. If the class is full when you try to register, keep trying; spaces will open up on a continuing basis if people drop before the semester begins. At this time, it looks like I will NOT be able to add additional students once the semester begins. If it will fit into your schedule, consider taking the evening section of Physics 101, which meets on Mondays and Wednesdays from 5:30 to 10:05.

Q: I've never taken physics before. Should I take some other, lower-level physics class before enrolling in Physics 101?

A: Not necessarily. Physics 101 is taught assuming no prior physics background. Those who have taken physics previously are, of course, more likely to be familiar with the vocabulary and concepts of physics, which may be helpful. However, this does not appear to be a major factor in determining how well students do in the course. In a typical semester, about half of the incoming students have had some physics before, and half have not; both groups tend to do about equally well overall.

A few students choose to take an algebra-based physics class, such as Physics 6, before enrolling in Physics 101. You may certainly do this if you like, but I honestly don't recommend it. I think there are better ways to spend your time and effort than taking two very similar courses, both of which are quite work-intensive.

If you haven't taken physics before and are concerned about preparing for the class, here's what I would suggest: Make sure you have the proper math prerequisites for Physics 101, as described above. If you have any trouble with written or spoken English, work on your language skills; consider taking an English class if you can, since verbal skills really are important for physics. Get yourself a copy of the textbook early, and start reading ahead so you'll have some idea what to expect when the class begins. Finally, please don't hesitate to email me if you have any questions or specific concerns.

Q: I preregistered for the class, but I won't be able to attend the first class meeting. Is that okay? What should I do?

A: Missing the first day of class is never a good thing, but I understand that sometimes an important commitment or an emergency can require you to do so. If this happens, the most important thing is to tell me you will be gone and explain your reason, so that your spot in the class will not be given away. I will then let you know what you've missed on the first day and how you can make things up. (Keep in mind that some activities require your presence in class and cannot be made up.) The best way to get in touch with me is by email.

Q: I didn't preregister for the class, and I didn't show up on the first day. Is there any chance I can still add?

A: I'm sorry, but no. There are a limited number of spaces in the class, and it's virtually certain that they will be filled on the first day. If you want a chance at getting in, come to the first class.

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Q: What textbook will be used for Physics 101? What other materials will be needed for the class, and where can I get them?

A: Our textbook will be University Physics, 12th edition, by Young and Freedman. (We will be making use of the online program Mastering Physics that is associated with this text.) The class also requires a set of workbooks, Tutorials in Introductory Physics, by McDermott and Shaffer (the set includes the main tutorial book plus a homework book). Finally, there will be a lab manual, which is based on the published book RealTime Physics: Mechanics, but has been locally modified to fit our equipment and curriculum.

The most convenient place to get your textbook is at the Pierce College bookstore. If you purchase a new book there, it will include a Mastering Physics access code, at no extra charge, and the tutorial books will be bundled with it. The overall price for the bundle is about $30 less than the cost of buying all three books separately. In addition, you will need to pay a lab fee at the bookstore for the lab manual, which is based on a published book but has been modified to fit Pierce's lab equipment and curriculum. The manual will be handed out in class once you have paid.

Another option for buying the textbook is to purchase ebook access from the Mastering Physics web site. The total cost for Mastering Physics plus ebook access is about $80, which is considerably cheaper than the traditional textbook. (You will be responsible for printing costs if you want to print yourself a hard copy of the text, though.) If you choose the ebook option, you will still need to purchase the tutorial books (at the bookstore or from an online seller) and pay the lab fee (at the bookstore only).

Note: if you're feeling a bit of sticker shock after seeing the price for the textbooks, it may help to know that the same text and tutorial books will be used for Physics 102 and 103 at Pierce. So if you're planning to go on in physics, these materials will serve you for two or three semesters. If not, you should be able to sell back the textbook at the end of the semester. If you need help paying for your textbooks or other college expenses, talk to the Financial Aid Office (in person in the College Services Building, by phone at (818) 719-6428, or online).

If you are interested in buying your book elsewhere, or getting a used copy, see below. Also see the section on the reserve copy in the library.

Q: What is Mastering Physics?

A: Mastering Physics is an online homework program developed by the publisher of our textbook. Each of our homework assignments will include some required Mastering Physics problems, as well as some problems that may be done for extra credit, and some that provide practice for the exams. Some of the online problems are based on those in the textbook, while others are unique to the program. Most assigned problems will have some numbers and terms randomized, so that no two people will get exactly the same answer for a given problem. If you type in an answer, Mastering Physics gives immediate feedback on whether you're correct or not, and sometimes gives preprogrammed hints.

Q: How do I get an access code for Mastering Physics?

A: If you buy your textbook at the Pierce bookstore, or purchase the correct version elsewhere, a free code will come with your book, in a cardboard insert that you will need to tear open. Otherwise, you will need to purchase the code directly from Mastering Physics, for $45. When you enroll on the Mastering Physics site, you will be given instructions on how to do this.

Q: What is the course ID for Physics 101 on Mastering Physics?

A: It is MP101WESSLINGS09.

Q: What do I enter for "Student ID" on Mastering Physics?

A: Enter your Pierce College ID number (a 9-digit number beginning with 88).

Q: What are clickers? Will we be required to buy them?

A: Clickers are small remote-control devices that will allow everyone to vote anonymously on multiple-choice questions during lecture. The voting process allows everyone to be engaged and active, serves as a starting point for discussions, and gives me feedback on what is understood and what isn't.

You will not be required to purchase your own clicker. In order to help save students money, the physics department has recently decided to purchase a set of clickers and allow students to borrow them during class. (If you already have a clicker from another class, you may certainly use it for Physics 101.)

Q: Is it okay to order the textbook online, or get a used copy?

A: Yes, and it may be possible to save money that way. However, if you do so, you are responsible for purchasing the additional required materials:

1. Mastering Physics is an online program that we will be using for some homework problems. Some versions of the book include a free access code; the ISBN of the correct edition is 080532187X. (This edition should be listed as "University Physics with Mastering Physics.") If your textbook does not include an access code, access may be purchased directly from the Mastering Physics web site, for about $45.

2. The tutorial books are also required. They are available from online retailers such as Amazon, as well as at the Pierce bookstore. However, they may not be bought or sold used, because they are workbooks that students write in.

3. No matter where you get your textbook and tutorial books, you are responsible for paying the lab fee at the bookstore, in order to cover the cost of the lab manual. (The lab manual is not available anywhere else, and cannot be bought used.)

If you decide to buy your books online, make sure to order them early--at least a week before class begins is best. "I don't have the book yet" will not be an acceptable excuse for extensions on assignments. If the class has already started and you have not yet obtained a copy of University Physics, I recommend using the reserve copy in the library.

Q: I have an older edition of the textbook. Is that okay?

A: The newer edition has made some helpful changes, including correcting a few glaring errors, improving the explanations of some concepts, and adding or changing the format of many examples. However, the basic content and organization of the textbook remain the same. As far as preparing for the reading quizzes and using the text as a reference, you should not have much difficulty with the older edition.

On the other hand, one thing that is definitely different in the new book is the homework problems: some are numbered differently, and others are completely new. If you have an older edition, make sure to check with a classmate or with a copy in the library in order to be sure you are doing the correct problems for each homework assignment. Full credit will not be given for doing problems other than the ones assigned. Also, as noted above, if you do not buy a new book, you are responsible for purchasing Mastering Physics access, the tutorial books, and the lab manual.

Q: Can I get the textbook from the Pierce library?

A: Yes. There is a copy of University Physics on reserve in the Pierce College library. You may check it out from the reserve desk for up to two hours at a time, any time the library is open (as long as no one else happens to be using the book then). Make sure to ask for the correct (12th) edition.

Q: What is a lab fee, and how do I pay it?

A: The lab fee, which is $32, covers the cost of your lab manual for Physics 101. Paying the lab fee is essentially the same as buying any other book, except that the process is a little different. To pay, go to the Pierce bookstore and tell the cashier that you need to pay a lab fee for Physics 101, section 0573. Once you have paid, you will be given a receipt. Show your receipt to me in class, and I will give you a copy of the manual, which contains all the labs for the semester. The first real lab will take place on Thursday, Feb. 19; it's a good idea to pay the fee by Tuesday, Feb. 17, so that you will have time to do the pre-lab.

Q: Instead of paying the lab fee, I'm just going to make a photocopy of someone else's lab book. Is that okay?

A: No, that is not okay. First, it is illegal: it's a violation of copyright law. Second, the physics department has already paid printing costs and royalties to the publisher so that the lab manuals could be produced; the price charged is necessary in order to cover these costs. (The department does not make any profit on this!) If you don't pay for the book, the department loses that money; if the college loses money, that will mean higher fees or reduced services for students in the future. Therefore, you will effectively be stealing from your fellow students if you do this.

Q: What are tutorials?

A: Tutorials are group activities that have been developed to improve students' conceptual understanding of physics. Each section of the main tutorial book includes a series of questions, and sometimes short experiments, that are designed to highlight and resolve confusing issues and to challenge your assumptions. Sometimes the questions look simple on the surface, but they are usually more subtle and interesting than they appear. During the tutorial periods in class, you will discuss these questions in small groups of 3-5 students. I will be there to guide you and steer you in the right direction, but I will not tell you directly whether your answers are correct. The idea is for you to come to conclusions on your own, based on logic and the laws of physics you have learned, and to reach a point where you have confidence in your own thinking.

The work that you do on the tutorials in class will not be handed in or graded. However, it is to your advantage to write down answers to the questions in as much detail as possible, so that you may later use them as a reference. You will be graded on the homework that corresponds to each tutorial, and each exam will include tutorial-like questions.

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Q: I really need to do well in Physics 101, because I'm planning to transfer or apply to a graduate program, and I won't be able to get in without a certain grade. How can I be sure to get a good grade?

A: You are not alone. Nearly all of my students are planning to continue their studies elsewhere, and need good grades in order to do so. I am willing to do whatever I can to help you earn the grade you want, but ultimately the responsibility is yours. Here are a few suggestions:

By far the biggest contribution to your grade in Physics 101 comes from exams. But this does not mean you should neglect other aspects of the class. Everything that is assigned or presented--reading from the textbook, attendance and participation in lectures, demos, tutorials, labs, and homework--will help you prepare for the exams. If you keep up with all the class work, relatively little last-minute studying should be necessary.

Homework is one of the most important forms of practice in this class; it prepares you directly for solving problems like those you will see on the exams. It also can provide an early warning sign that you may be having trouble. It's quite common to read through a chapter in the text, nodding along and thinking that it all makes sense, but then be unable to explain or apply the concepts in a homework problem. This is a sign that you don't really understand the material as well as you thought. It doesn't mean there's anything wrong with you. That's the way the human mind works: we can seldom learn anything until we've practiced it.

If you can't figure out how do the homework problems, resist the temptation to copy someone else's work; even if I don't penalize you for cheating, you'll learn little or nothing that way, and will end up doing poorly on the test. (Learning physics needs practice, just like sports or music: would you prepare for a game or performance just by watching someone else play, without any practice of your own?) Instead, please ask for help! Come to office hours, stay after class, or email me with questions. You may also want to work together on the homework with your fellow students, or consult a tutor at the Learning Center.

After each exam, I will print out spreadsheets showing everyone's grade thus far. If you are not happy with your current grade, talk to me to find out what else you can do. The most important thing is to ask for help early in the term. I'm very willing to help you learn as much as possible during the class; I will not be at all willing to change your grade once the final grades have been assigned.

Q: When are your office hours?

A: They are listed on the main page. At these times, I am guaranteed to be in my office; you need not make an appointment in advance. If you would like to meet with me at another time, please email me or talk to me after class.

Q: Won't I be bothering you or interrupting your work if I come to office hours?

A: Absolutely not. The entire purpose of office hours is for me to help students. Please come by; I'll be glad to see you!

Q: Do you take effort into account when assigning grades? How can I make it clear that I'm putting in extra effort?

A: Yes, effort is a factor. I grade on a fixed scale rather than a curve (90% and above is always an A, etc.), but if you are close to the borderline and have clearly made an extra effort, I will be generous in assigning your grade (e.g., an 89% could be an A).

How do I know if you're making an extra effort? One good indicator is that you ask me for help when you need it; this shows me that you're really trying to understand the material and are putting some thought into your assignments. Other good things to do: speak up in class discussions, take on an active role in group activities, take extra care in making your written work clear and detailed.

Q: Do you give extra credit?

A: A limited amount of extra credit is available to everyone, in the form of additional online problems that you can do to improve your homework grade. I generally don't believe in assigning large amounts of credit for extra projects, however. If you are struggling, I think your time is better spent in trying to improve your understanding of the core material in the class, rather than doing something outside of the regular curriculum.

Q: About how many hours per week should I spend studying for Physics 101?

A: The answer to this varies somewhat from person to person. Many experts recommend about 2-2.5 hours' study outside of class for every hour spent in class; this applies more to lecture-based classes than to lab classes, so it requires some thought to decide how to apply it to Physics 101, which is a combination of lecture and lab. As a very rough guideline, I would suggest about 10 hours of study per week outside of class. This may include time spent reading the textbook before lectures, doing homework and practice problems, reviewing labs and homework solutions, and going over your lecture notes. Of course, some people will find that they need more time than this, while others can get by with less. The most important thing is to spread out your study time; do a little each day, rather than a huge marathon right before the exam and nothing at all on other days.

Q: What's the best way to prepare for exams?

A: There is really no single "best" way; different people have different styles of learning that work for them. But I can offer you some guidelines that are likely to be helpful:

1. As mentioned above, most of your preparation should occur well before the exam: doing homework, participating in tutorials, labs and lectures, etc. Keeping up with the day-to-day class work is one of the most helpful things you can do. Start assignments as early as you can, and ask for help if you need it. Some of the homework problems are taken from old exams; they will be particularly helpful in showing you what the exam will be like.

2. The labs are very important in preparing for the exams. During the lab, make sure that you answer the questions on your own copy of the lab manual, even if yours is not the one that gets handed in; you can then use it for reference when studying. Also, when the graded labs are handed back, make sure you get to see and make note of the comments on your group's report. The lab homework is a good indicator of how well you understood the concepts in the lab. If the homework seems overly difficult, you may want to spend some time going over the lab with me or with your classmates.

3. The tutorials will likewise be important, since each exam will include a significant conceptual component as well as quantitative problems. The work you do in your tutorial book during class will not be graded, but it is to your advantage to write down detailed answers and explanations so that you may study them later.

4. One of the best things you can do is to practice what you will actually be doing on the exam: solving problems and answering questions. If you got any of the homework problems wrong, or skipped them, go back and try to do them again without looking at the solutions, following the problem-solving procedure that we'll discuss in class. Then, go over the solutions and compare with your results. Look through labs and try to make the predictions without looking ahead; go through questions from the tutorials with a classmate. There are many extra problems on Mastering Physics that you can do for practice. I'll also post the clicker questions from lecture on Moodle; try to answer them without looking at your notes.

5. Making your formula sheet can be a very useful review. Don't just go through the chapter and write down every equation you see; decide which ones are important and which are too specific to be helpful. For each equation you include, ask yourself: What does each symbol represent? What units is that quantity measured in? Is it a scalar or a vector--and if it's a vector, what does its direction tell me? How did they come up with this equation--is it based on other laws of physics? Was it derived assuming specific conditions (e.g., constant acceleration, no friction, etc.)? When is it applicable, and when not?

6. Rereading the textbook is usually not a very productive method of studying, unless you do it in an active way: start each section with a question in your mind that you're trying to answer. The authors have helpfully added multiple-choice review quizzes at the ends of most sections; look at the quiz first, and read through the section with the intent of finding the answer. You can also make up your own questions, based on the section titles or examples that have confused you.

7. Sleep. Seriously! There is experimental evidence to back up this advice: studies have shown that people did a better job learning a task when they were tested on it after a full night's sleep, compared with a control group who were tested after waiting for 12 hours but not sleeping. You'll be much better off getting a good night's sleep the night before the exam, rather than pulling an all-nighter to get in some last minute cramming. Once again, memorization is not very important for doing well on the exams; it's much more important to have your brain alert and functional when you take the test.

Q: Will this be on the test?

A: My answer to this question is always yes. If "this" is anything that has been covered in any way--reading assignments, lectures, demos, labs, tutorials, homework--then it is fair game for a test.

Q: Where can I find answers to questions about grading policy? For example:
How much does each type of assignment contribute to my grade in the class?
How many test or assignment scores will be dropped?
Is late work accepted?
How are extra credit scores counted?

A: The answers to all of these can be found in the syllabus.

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Q: I heard that physics is really hard. Is that true?

A: I get this kind of reaction a lot, both from students and from random people I meet in daily life. I'd like to try to give a careful answer here. First, I have the impression that a lot of people think something like this: "Physics is so hard that only a few super-geniuses can possibly do it. Ordinary people have no hope of understanding it, and shouldn't even expect it to make sense." That is emphatically NOT true. Anyone with the proper mathematical background can, with appropriate effort, learn to do physics and make sense of it. Depending on the type of physics and the level of sophistication desired, "proper mathematical background" might have a wide range of meanings; many of the fundamental ideas of physics can be understood, at a basic level, with no math at all. For Physics 101, the proper mathematical background is a knowledge of basic calculus. If you have this math preparation, you are fully capable of learning and understanding physics at this level. No one should feel intimidated by the prospect of taking this class. If you come in assuming everything is going to be very hard, this may create a psychological barrier that causes you to make things more difficult than they really are.

On the other hand, that phrase "with appropriate effort" is key. Physics is hard, in the sense that it demands labor from you. Physics, just like music or sports, cannot be learned without practice. And practice, just as in music or sports, is not always fun. It requires doing difficult tasks and repeating them over and over until you get them just right. The fun part (I hope) comes when everything clicks into place and you understand how and why some aspect of the universe works.

Also, many people come in with the misconception that they can do well in physics if they can just memorize the right things. Memorization is actually much less important in physics than in many other subjects. (You will not need to memorize any equations in my classes, because you will be allowed to refer to a formula sheet during exams.) Physics is much more about logic and reasoning than it is about remembering a list of facts. Someone who is very good at memorization may be used to doing well on exams, but will find that this skill doesn't help so much on a physics exam.

Q: When solving a physics problem, how do I know what equations to use?

A: This is maybe the most frequently-asked question of all. I'm afraid I can't answer it in the way you may be hoping. There is no arcane set of rules to memorize, like "If it's Tuesday, and it's an even-numbered problem, and the question uses the letter 'r' at least five times, then you should use E = mc²." As noted above, physics is not about memorization; it is about logic and reasoning. The only way to figure out which equation, or equations, to use is to understand what's physically going on in the problem, and to connect that to an appropriate mathematical picture.

If you are asking this question, you have hit on one of the most important issues in learning physics, but you might be in need of a shift in perspective. The question "what equation should I use?" suggests a belief that the real heart of a physics problem is plugging numbers into an equation and getting another number out; this would be so much easier if there were a quick way to get past that fluffy bit of choosing which equation! But any physicist will tell you that plugging in the numbers is almost an afterthought; the most important part of the problem is actually choosing, or deriving, a formula to use. A better phrasing: a physics problem is about analyzing a situation in terms of a few basic laws, usually with the help of a mathematical model. Such a model is usually expressed in terms of one or more equations. Equations are not mystical 'black boxes' that work in mysterious ways; they are statements about relationships between things, expressed in a mathematical language. If you truly understand what an equation means, and where it comes from, you can always figure out when to use it. When starting a problem, the first question you should ask is not "What equation should I use?", but rather "What's happening in this problem? What ideas are relevant?"

Here's a very simple example: if you drive at 50 miles per hour for two hours, how far have you gone? Most people can answer this quickly: 100 miles. Where does this come from? During each hour, you traveled 50 miles; since you drove for two hours, (2 hours)*(50 miles/hour) gives 100 miles. We can easily generalize this for any speed and time:
d = vt,
where d is the distance traveled, v is the speed at which you're traveling, and t is the amount of time you spent. You have quite likely seen this equation before, perhaps in an algebra class. It's not an equation anyone should need to memorize or look up; if you understand what "speed" means, this relationship follows immediately. A speed tells you how far you'll travel in a certain amount of time (e.g., how many miles covered in each hour); multiply that by the amount of time you traveled (e.g., the number of hours), and you find out how far you went (e.g., the number of miles). Once you have this equation, you can do any sort of algebra you want; if you were given the distance and the time, for example, you could solve for the speed.

It should also be clear that this equation has limitations: it only works if you were going the same speed the whole time. (If you had different speeds at different times, how could you decide what to plug in for v?) If your speed changes, you need a more complicated equation, something that contains information about how the speed changed (i.e., about acceleration). Nearly all equations have such limitations; they make sense in some situations, but not in others. The derivation of (steps for coming up with) any equation should make it clear when it is valid and when not. Obviously, not all equations are this simple to derive, but they all come from someplace--your textbook usually explains where--and they all have physical meanings that tell you when they can be used.

Often, people are confused by the sheer number of equations that appear in a textbook. Bear in mind that not all of them are equally important! Many equations you'll see are just special cases of some more general formula. Each chapter of the book is organized around a few basic principles and definitions. (In mechanics, these include Newton's laws of motion, conservation of energy, and conservation of momentum.) The equations that define these are highlighted and prominently displayed; if you look carefully at the book's examples, you'll see that they nearly all start with these same few formulas. An equation that shows up in the middle of an example, and never appears again in the book, is probably very specific to that example; it's much more important to see how they came up with that equation than it is to remember the equation itself.

Q: I have a question about Physics 101 that was not answered on this page. What can I do?

A: Please email me with other questions, and I will do my best to answer them.

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FAQ for Physics 101

Basic info: what is it?

Registration

Textbooks and other required materials

Grading, studying, and exams

Metaphysical questions: how to approach physics, and why it matters

Other questions