The chemical energy in your breakfast becomes the motion of your legs, which becomes heat as you run. Energy constantly changes costume — chemical, motion, heat, light — but the total never vanishes; it's only transformed.
Stored energy and moving energy
Energy is the ability to make things happen. A ball held up high has potential energy — stored, ready to go. Let it drop and that stored energy becomes kinetic energy — the energy of motion. The higher you lift it, the more it has to spend on the way down.
Energy only changes form — it never disappears. A roller coaster trades height (potential) for speed (kinetic) and back again. Even the energy lost to friction just becomes heat.
- Kinetic — motion (a rolling ball, blowing wind)
- Potential — stored by position or shape (a raised weight, a stretched rubber band)
- Thermal, light, sound, electrical, chemical — energy wears many costumes
- Tie a small weight to a string to make a pendulum. Pull it up to one side and hold it.
- Where is its energy stored right now — as motion or as position?
- Let go. At the very bottom of the swing, what kind of energy does it have most of?
- Watch it climb the other side. Track where potential is highest and where kinetic is highest.
What you should see: You watched energy trade back and forth between potential and kinetic — highest potential at the top, highest kinetic at the bottom.