Energy
What is stored, what is spent, and what it turns into.
Lift something and you store energy in it; let it go and it turns into movement. Stretch a spring and you store energy in that; let it go and the same thing happens. Energy is never made or lost, only moved about and, eventually, turned into heat, where it stops being useful.
| Store | How it is worked out | Unit |
|---|---|---|
| Height | mass × gravity × height | joules |
| Movement | ½ × mass × speed² | joules |
| A spring | ½ × stiffness × stretch² | joules |
The app reads the board's total kinetic energy at the bottom of the window, and a meter can read it for one body. Watch it on a pendulum: all of it is height at the ends of the swing and all of it is movement at the bottom, and with damping turned off the total holds steady.
Open the ramp scene in the app to watch this one run.