How to study for a physics exam

A physics exam is mostly problems, so it is tempting to prepare by reading worked solutions until they make sense. That feels productive and does not transfer well. Following a solution and producing one from a blank page are different skills, and the exam only tests the second. Many lost points in an intro course come from a few predictable places: an equation you can't recall, an equation used outside the conditions it needs, a sign flipped halfway through, or an answer nobody checked. Each of those has a specific fix.

Learn each equation with its conditions

Knowing R = v0^2 sin(2 theta) / g is not enough. You also need to know it only works when the projectile lands at the height it was launched from. The four kinematic equations only hold for constant acceleration. Momentum is conserved in a collision when no net external force acts, but kinetic energy is conserved only if the collision is elastic.

So memorize equations in pairs: the formula and the condition. A good flashcard asks "when can you use R = v0^2 sin(2 theta) / g?" as well as "what is the range formula?" The first question is the one that saves points. Projectile motion equations with worked examples shows how badly the range shortcut fails from a cliff: 19.9 m instead of the real 38.0 m.

Symbols and units belong on the same cards. If you can't say what each letter in P = rho g h means, or what unit it comes out in, you can't use it under time pressure.

Solve problems with the same routine every time

OpenStax College Physics 2e (section 2.6) gives a problem-solving strategy that works for the whole course:

1. Examine the situation and sketch it.
2. List what is known, with units.
3. Identify exactly what you are asked for.
4. Choose an equation that connects them.
5. Substitute with units and solve.
6. Check whether the answer is reasonable.

Steps 1 to 3 are where most mistakes are prevented. Write down "up is positive, a = -9.80 m/s^2" before any algebra, and the sign errors mostly go away. For dynamics, the sketch is a free-body diagram, and many wrong answers in Newton's-law problems start with a missing or extra force on it.

Use the routine even on easy problems. The point is to make it automatic, so it is still there when a problem is hard and time is short.

Practice from a blank page

Cover the solution, attempt the problem, then compare. If you get stuck, look at one line of the solution, cover it again and keep going. Retrieval practice (pulling an answer out of memory instead of rereading it) builds memory in a way that recognizing an answer does not. The testing effect covers the research, and the illusion of competence explains why rereading solutions feels better than it works.

The same goes for concepts. Say out loud why the velocity at the top of a throw is zero while the acceleration is still 9.80 m/s^2 downward. If you can't explain it without notes, you don't know it yet.

Mix problem types before the exam

Homework sets come sorted by chapter, so you always know which equation to use. The exam does not tell you. A block sliding down a ramp could be a Newton's-law problem or an energy problem, and choosing is part of the question.

After you've learned each topic on its own, practice mixed sets: a kinematics problem, then an energy problem, then a momentum problem. It feels slower and harder, which is the point. Interleaving vs blocking explains why mixing helps.

Check every answer three ways

Before moving on, spend ten seconds on these:

• Units. If a distance comes out in m^2/s^2, you forgot a square root. If a force is not in newtons (kg m/s^2), something is off.
• Sign. A falling object moving upward, or a braking car speeding up, means a sign slipped.
• Size. A thrown ball doesn't go 800 m. Compare against things you know: a car braking from 20.0 m/s at 5.00 m/s^2 needs 40.0 m, and from 40.0 m/s it needs 160 m. If your answer is wildly off from a sanity check like that, go back.

Special cases help too. Set the angle to 90 degrees in a level-ground projectile answer and the range should come out zero, because the ball goes straight up and comes straight down. Set the acceleration to zero in a kinematics answer and it should reduce to distance = speed x time.

The kinematics calculator and projectile motion calculator show every step of the working, which is useful when your answer doesn't match the key and you need to find which step went wrong. For unit problems, the unit converter helps.

A two-week plan

Two weeks out. List every topic on the exam. For each, write the equations and the conditions from memory, then check against your notes. The gaps you find are your study list.

Days 13 to 6. Work through topics in course order, a few problems each, from a blank page. Review equation cards every day so the early topics stay fresh while you work on the later ones. What spaced repetition actually does explains why short daily reviews beat one long session.

Days 5 to 2. Mixed practice under time limits. Take an old exam if your instructor posts one. Redo every problem you missed a day later, from scratch.

The day before. Light review of equations and conditions, a few mixed problems, then sleep. How to build a study schedule before an exam covers the general version of this plan.

For a final exam, remember that physics is cumulative: energy uses kinematics and Newton's laws, and rotation repeats the whole first half with angular quantities. Old units need review even if they felt easy at the time. See studying for a cumulative final vs a unit test.

On exam day

• If you're allowed an equation sheet, write it yourself. Writing it is study time, and you'll know where everything is.
• Do the problems you're sure of first, then come back to the rest.
• Show your setup. Many instructors give partial credit for a correct diagram and equation even when the arithmetic goes wrong.
• Keep units through the whole calculation, not just at the end.

Where to start

What's in College Physics I lays out the course topic by topic, and the four kinematic equations and when to use each is a good first unit to drill. Taking chemistry at the same time? How to study for a general chemistry exam covers the same ideas for that course.

Every equation, condition and common mistake in the course is in Encodr's free College Physics I deck, scheduled for review so it's still there at the final.