Puzzle #10: Physics Stumpers
You have a piping hot cup of coffee that’s too hot to drink. You can either pour a splash of cold milk into it and then let it sit for 10 minutes, or first let it sit for 10 minutes and then add the milk. In which scenario will the coffee end up cooler, or are they equivalent? In both scenarios, assume you pour the same amount of milk and it is the same temperature.
You’re in a canoe in the middle of a pond and you brought a rock with you. You pick up the rock, drop it into the water, and watch it sink to the bottom. Does the water level of the pond rise or fall (however imperceptibly) when you do this, or does it stay the same?
More knowledge of physics will make these puzzles easier, but you should test your intuitions regardless of your background. Each problem demonstrates a different physical concept, and they have elegant solutions that don’t require calculations. You could even take a proud plunge into empiricism by running the experiments for yourself—please let me know if anybody does this.
Find the solution at the bottom of this page.
