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Asaf Pe'er

Tips for Exmas

After looking at enough student's exams, I feel I have a few useful tips for students....


Plan ahead - 1. Roughly, about 85% of those who failed an exam, also failed in the problems given as homework. Your ability to solve the problems during the semester is your best indication of how well you are going to do in an exam. Do not expect miracles !. Do not delay your studies until the last week or so. It simply doesn't work like that at a university level. If you feel that you don't fully understand the material taught in class, ask !! . You have plenty of time during the semester - studying a few days prior to the exam is simply too late. (Needless to say, do not copy the homework - you may "save" time, but you are BADLY HURTING YOURSELF. For the extra few credit points you may "earn" by copying the problem set, you will pay heavily when it comes to the exam !).

Plan ahead - 2. There is a limited time in the exam, and you have several questions you have to solve. It is a bad idea to get "stuck" on one question. Better to get partial answers to 3 questions, rather then a full answer to only one question. In particular, when there are 2 sections - some people are doing very well on one section, and very poor on another. Much better to be balanced - you will earn more points.

Physical Insight. You are studying physics. You are expected to show that you understand physics, at some level. Thus, after you finished answering a question: always look at your final answer: does it make sense ??? Did you use the correct units ? Classical examples:
- In a question about relativity, clearly if you ended up with something that travels faster than light, you did something wrong.
- Use your "common knowledge": for example, I asked once about the speed needed for an airplane to take off. Without getting into the details, clearly if your result is something like 5 cm / second, or 30,000 km / second, you are wrong.
- When plotting a phase diagram, there were students who confused liquid and gas (more likely, they just guessed). Thus, in their diagram, increasing the temperature made a gas convert into liquid !. Such a mistake reflects badly on the assesment of the exam.
And what if you discover a mistake but don't have time to correct it? At least, write on the script that the result you got looks fishy to you. It will show that you understand something, and most likely will earn you some credit.

Answer the question !. Read carefully the question, and make sure you answer what is asked, and not something else. I don't get impressed by stories. If you write all sort of related things but you don't answer the question, you will not get points.

Explain what you try to do. State clearly (in words) what you are calculating. Sometimes I get answers like "x=7", with no explanations. If this is the wrong answer, clearly you don't get any points, but even if this is the correct answer, I can't tell that you are not cheating. If I know what you are attempting to do and there is a mistake somewhere along the way, you get partial credit (sometimes even full credit, if it is a small mistake).

Put numbers at the end. When you have some calculation to do, it is nearly always MUCH easier to work with the variables (x,v, or whatever), and only when you get to the final line, put the given values and write the final answer.

Do not memorize. Think. Unfortunately, too often students try to memorize derivations, homework, etc, and then use them in the exam, although the question is different. Unfortunately, this is often not very helpful at University level exams. You need to show that you understand, and for that you have to think.

When plotting a graph, always mark the axes. Sounds trivial.

Check units ! You can avoid enumerous amount of mistakes by simply looking at the units of your answer. Say, if you calculated velocity and got units of [meter], you know it is wrong.

Write clearly. Think of it from my perspective: I have to grade tens, sometimes hundreds of exams. It can get quiet annoying if I need to start deciphering impossible hand writing. The clearer you write, the easier it is for me to understand what you meant - the more likely I will "forgive" you for a small mistake.

No need to change units. Unless directly asked, normally there is no need to change units. For example, if all the velocities in a question are given in km / h, you can put your final result in km / h - no need to convert to, e.g., m / s. It just increases your chance of mistake.

Master the baic mathematical skills. Part of your practicing homework is to ensure that you fully master the basic skills needed from a physicist. I do expect second year students to be able to carry elementary calculations such as e^0 (=1) or a little more complicated ones such as d/dt (e^{a/t}). If you don't feel comfortable with the math, practice !!.

Good Luck !!