Recommendations on how
to do physics
Doing physics problems develops several very
useful skills that will help you way beyond your physics education.
importantly, these include organizing your thinking and communicating
your results. These are skills that are acquired only by practice.
of it! Below are recommendations for how to do physics homework. Some
suggestions will be more relevant than others depending on the specific
Very important: If you are confused
particular topic, you will probably find that it is difficult to
question to ask. Formulating a good question is 95% of learning
best way to learn is to discuss physics with other people. Talk to your
classmates, and do not be afraid to
seek help from the professor or the tutor just because you don’t
specific question. Simply discussing things will help.
It is very common for students
to find physics problems to be hard, and then very suddenly, when
you make a conceptual breakthrough, they become easy. Strive for this
experience and don't give up.
- Use unbound blank paper. Don’t
let the paper you use restrict your thinking.
- Begin by thinking in terms of principles,
not in terms of which formulas you need.
- Organize your thinking by drawing
a picture of the situation. This is by far the most
useful way to approach a problem, and is the “secret” to
- Pick a coordinate system and use
it. This is how you connect what the problem gives you to the
variables in your formulas. You should have a very clear idea of how
every term in your formula relates to the coordinate system.
- Make sure you understand what is known
and what needs to be determined. Make a list, and assign variable names
to the unknowns.
- Make sure you understand the units
being used. Convert if needed. All those numbers have a meaning, and
sometimes problems pick funny units to try to trick you.
- Believe it or not, it really is easier
to manipulate formulas first, then plug in numbers at the end. This
makes it easier to go back and correct any mistakes you may make, and
is the best way to earn partial credit if you can’t solve the
- You need to communicate your
line of thinking to the grader. Simply getting the right answer
is not enough. Be neat and clear. Don’t be afraid
to use words to describe your approach.
- Ask yourself if your answer is reasonable,
both in terms of magnitude and units.
- If you need to make assumptions, state
- Staple your pages together.
- Discuss your homework with
others. Form study groups.
- There are often several ways to solve
a problem. Use the methods described in the chapter to answer
problems from that chapter.
will be useful later on in the semester)
- Keep in mind the difference between scalars
and vectors. If your answer is a vector, you must report both a
magnitude and a direction.
- Advice on drawing free-body diagrams:
Remember that the two forces that
Newton’s third law refers to act on two different objects!
When calculating work, be clear about
what force is doing the work, and what object the work is being done on.
- It is often helpful to depict the
object in question as a point (unless torques are involved). Draw the
force vectors as arrows that come out of this point.
- Only include forces. Other vectors
such as acceleration or velocity should not be on a free-body diagram.
- Only indicate forces that act on
the object in question. Forces that the object exerts on other things
are not relevant for this diagram.
- When you draw a force vector, ask
yourself: “Where does this force come from? What other object
gives rise to it?” If you can’t answer this question, then
erase that force! Either that force isn’t real, or you’re
not using an inertial reference frame.
- Don’t blindly refer to
“the normal force.” Make sure you can answer the question
above before drawing it in.