Forces Doing Work: Energy and Power
Energy gets transferred whenever forces make things move - think of pushing a shopping trolley or lifting your school bag. When you apply a force over a distance, you're doing work, and work is simply energy being transferred from one place to another.
The work done equation is straightforward: Energy = Force × Distance. This tells you exactly how much energy you've transferred when you move something. There are several ways energy gets transferred around us: mechanical work (like pedalling a bike), electrical work (charges flowing through circuits), heating (due to temperature differences), and radiation (energy travelling as waves like light or microwaves).
Here's something brilliant about energy - in a closed system, energy never disappears, it just changes form! When a toy car rolls to a stop, its kinetic energy doesn't vanish; it transforms into thermal energy through friction.
Power measures how quickly energy transfers happen, calculated as work done ÷ time. It's measured in watts, where one watt equals one joule per second. Your phone charger might be 20W, meaning it transfers 20 joules every second.
Key Insight: Efficiency = useful energy ÷ total energy - this shows how much input energy actually does what you want, rather than being wasted as heat.