Physics Homework Tips – What Every Student Should Know

Empty Classroom
Once class is out, you’re on your own for homework. Don’t panic. Here are a few tips to make homework easier for physics (and engineering) students. Credit: Anthony J. Bentley/Creative Commons

Homework isn’t anyone’s favorite pastime. It’s something all students have to do at one time or another. While you may not enjoy it, homework is a beneficial part of learning physics. If you’re not careful, you may start to really understand the concepts you heard about during your lectures. Now that you have your work in front of you and everything else away from you, here are a few tips to help get through your problem sets.

Don’t procrastinate.

The first shock many first-year students receive is the first homework assignment. Your instructor wrote a list of problems maybe 15 long, and half of them were odd-numbered. Odd-numbered questions usually have answers in the back, so how hard can this be? Then you were told you would have over a week before they are due. If you are like most people, you will immediately file their homework in the ‘do later’ category and forget about it until the night before it’s due. Then you discover that nearly all of those questions have multiple parts that require correct answers from the first part. Your 15 problem assignment is actually closer to a 30-40 problem assignment. What do you do now? You hopefully just learned your first hard-earned physics lesson: Do NOT wait until the last moment to start.

Lose the distractions.

When you do begin to work on your assignment, work somewhere where you will not be distracted. Turn off the TV, computer, phone, or anything else that may break your concentration. You’ll find you learn a lot more when you are paying attention to the task at hand.

Write down what you know.

List your variables and write down their given variables. This helps prevent the casual use of a variable that could have two meanings. For example, d is often used as ‘distance’ but could also be a ‘diameter’. Listing your variables helps avoid this.

Sketch a diagram of the problem.

No one says you have to be an artist, but a clear, accurately labeled illustration can help you visualize the problem, and drawing the figure can help formulate the problem in your mind. Draw to scale if possible, label your variables, and include the values you know.

Choose your coordinate system wisely.

Align your coordinates along a path where some quantities will equal zero or variables will cancel out, reducing what you need to calculate. Also, choose a coordinate system appropriate for your type of problem. Linear motion? Cartesian coordinates may be your best bet. Angular motion? Radial coordinates. 3D field equations? Spherical coordinates. Choose a system that helps avoid unnecessary calculations.

Watch your vectors.

One of the most common errors in a physics homework problem is forgetting a vector is a number AND a direction. This error typically manifests itself as a sign error. Make sure your directions coincide with your coordinate system.

Use approximations.

Occasionally your problem can be simplified by approximations. The mass of a single electron doesn’t really matter when comparing to the mass of a desk. For this type of situation, treat the mass of the electron as zero. Another common approximation is sin(θ) ≈ θ for small angles (less than 3°).

Save numerical calculations until the end.

Work the dimensionless part of the problem first. Plug in any numerical values for variables once you have your answer in a simple formula. This will save needless calculator work and help prevent simple math errors.

Check your units.

Nothing can ruin your day faster than calculating an answer only to get it wrong because your units don’t match. Make sure all your units are the same across the problem.

Check your answer.

Plug your answer back into the original equation. Does your answer balance your equations?
Also, check to see if your answer makes sense. It sounds silly, but if your solution’s velocity is faster than the speed of light or the distance between planets is only 30 meters, maybe that should tell you something.

Final Bonus Tip: Pay attention in class.

Your instructor did not pick the assorted problems because they were easy to grade. It is more likely they closely follow what you should have learned during the lectures. If you picked up on the concepts from class, your homework should be much easier.

Homework is a large part of the process of understanding any topic. Why make it more difficult than it has to be? These physics homework tips should help you with your homework assignments and make learning physics easier.