Physics · Glossary

What is Energy?

Definition 29.1 Primary & Middle School Physics · Chapter 29 — Energy in Everyday Life

Energy is what it takes to make things happen: to set things moving, to lift them, to light them up, to warm them, to make them sound. Nothing goes, glows, or grows without energy being spent on it — and whatever is doing the spending must first have energy to spend.

Examples

Example 29.5 (Forms of energy)

Energy shows itself in different forms: motion energy in the rolling ball and the blowing wind; light energy pouring from lamp and Sun; heat energy in everything warm; electrical energy traveling through wires; stored energy waiting quietly in food, fuel, springs and lifted things. Same something, many forms.

Example 29.8 (Chains everywhere)

Your morning ride, traced: breakfast (store) \to your muscles (converter) \to motion of the bicycle ++ warmth (you feel it — you glow). The wind farm: moving air \to turning blades \to electrical energy in the wires \to light in your lamp tonight. The dam: high water \to falling water spins the turbines \to electrical energy. Long chains are just short ones linked: form after form after form.

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