Mistake Master
Mistake Master · AP Physics 2 · Unit 9 · Step-Through Animation
The Law That Supplies the Arrow
You'll learnto test a process against both laws rather than one, to read an entropy rise as energy spreading out rather than going missing, and to draw the boundary before judging a decrease.
Coffee cooling in a room balances the energy books exactly — and so would coffee heating itself back up, which never happens. Sixty molecules released from half a box will show you what actually chooses the direction. Twelve short steps; press Next for each one.
sixty molecules choose the direction · spread out is not destroyed
Before you start
What you're looking at
A cup of coffee cooling in a room, and a box of sixty molecules released from its left half, with a plot counting them.
The question
Energy is conserved in both directions of every process, so what decides which direction actually happens?
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