Physics

Motion & Forces

Mechanics formula sheet

Oscillation

Waves reference

Amplitude determines a wave's intensity (loudness/brightness); frequency determines pitch/color.

Circuits

Electricity reference

Reference

Unit conversion basics

Always track units through a calculation

Write units next to every number and cancel them like fractions - if the units left over don't match what the question asks for, a step is wrong.

SI base units to know

Meter (length), kilogram (mass), second (time), ampere (current), kelvin (temperature). Most other units are combinations of these.

Common prefixes

kilo- (×1000), centi- (×0.01), milli- (×0.001) - memorize these and you can convert almost any metric unit.

Common Mistakes

Where students go wrong in physics

Patterns we see again and again in student work. Each one is fixable once you know to look for it.

Starting with a formula instead of a diagram

The most reliable physics habit is to draw the situation before writing any equation: a free-body diagram for forces, a labelled sketch for kinematics, a ray diagram for optics. Most wrong answers in mechanics come from a force that was forgotten or pointed the wrong way, and a diagram catches that before the algebra starts.

Dropping units mid-problem

Carry units through every step. If your final answer for a velocity comes out in kg·m, you have caught an error you would otherwise miss. Units are the cheapest error check in physics, and they are free.

Confusing mass and weight

Mass is measured in kilograms and does not change. Weight is a force, W = mg, measured in newtons, and depends on gravity. Problems that give you mass and ask about forces require the conversion; problems that say "a 50 N object" have already done it.

Treating vectors as numbers

Velocity, force, and acceleration have direction. Two forces of 10 N do not necessarily add to 20 N. Resolve into components, work each direction separately, and recombine at the end. Sign conventions (which way is positive) should be chosen at the start and never changed mid-problem.

Memorizing which equation to use by the problem wording

Kinematics equations are chosen by which quantity is missing. List the known variables, list what is asked, identify the one variable not involved, and pick the equation that leaves it out. This is a mechanical procedure and it beats guessing every time.