Energy and electricity

Energy is the idea that ties most of physics together, and this topic shows how to calculate it and track it. You start with kinetic and gravitational potential energy. Kinetic energy depends on the speed squared, so doubling the speed makes the energy four times larger, and forgetting to square is the most common slip. Next is conservation of energy: energy is never used up, only transferred or changed from one store to another, so the total before equals the total after. Many problems become one line once you set those equal. The final page is Ohm's law, V = IR, the first formula most students meet for circuits. The mistakes here are rearranging it incorrectly and mixing up which quantity is which. Keep units at every step: joules for energy, volts, amps and ohms for circuits. If an answer comes out in the wrong unit, check your formula before you check your arithmetic. Then try the three practice questions on each page.