Where Energy Goes: Friction and Heat

Lesson 5 of 10 · 7 min · Free, no account needed

What you will learn

Friction and bumps turn useful energy into thermal energy (heat): warm wheels, brakes, a warm ball and floor.
Energy is never lost, only spread out. Height + motion + heat stays the same total.
A machine can never put out more energy than goes in. Spread-out heat is hard to use again: this is dissipation.

A bouncing ball bounces lower every time. Where does the missing energy go?
First, your guess: drag the five markers to the heights of the next five bounces.
Turn up the friction and let her ride. Watch the new bar.
Now the real ball. Press Play and compare it with your guess.
The missing energy has a name.
Thermal energy is the energy of jiggling particles: we feel it as warmth. Friction, squashing and bumping turn other energy into it.
Energy is never lost, only spread out. With friction: height + motion + heat = the same total.
Heat spread through a floor or the air is very hard to collect again. Losing useful energy this way is called dissipation.
Where does most of the energy end up? Sort each example.
Game: Patent office. Approve honest machines, reject impossible ones.
Test each machine, then judge it. Four patents.
Code: in this game the ball bounces for ever. Tap the bounce line to make it lose energy.
Then Check: the program runs and draws the height.
A bike brakes to a stop on a flat road. Where did its motion energy go?
Tap the store, then Check.
Your bounce prediction against the real ball. Press Play.

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