You can find the answers to our Christmas Puzzles in the videos below!
Puzzle 1
It’s Christmas morning and a sleepy physics student fancies an untraditional egg sandwich for breakfast. They open the fridge door and see two identical looking eggs inside. They remember one is raw and the other is a hard-boiled egg from the day before. Unfortunately, they can’t remember which is the hard-boiled egg and nobody wants a raw egg sandwich! Without using any gadgets or breaking the eggs, how do they determine which is the hard-boiled egg?
Solution 1
The eggs both look the same, they both weigh the same, and if I were to put them in water, they would both sink. What we have to focus on is the difference between them and the difference is that one is solid and the other one isn’t; it has a yolk inside that can move. Therefore if I were to spin one of these eggs, so it’s spinning and then stop it with my finger, just long enough to stop it and then let go, then the hardboiled egg should remain stopped, but if the egg is raw, the yolk will still be spinning and so when I let go of the egg, the egg should continue to rotate just a little.
Solution to Puzzle 1
Puzzle 2
After breakfast it’s time for presents! The physics student finds three boxes on the table. Their parents tell them one box has a new iPhone in and the others are empty. To get the iPhone they must guess which box it is in! They pick one box at random; then their parents open one of the remaining boxes to show it is empty and ask the physics student if they wish to change their mind. Does switching alter their chances of getting the iPhone? Why?
Solution 2
Solution to Puzzle 2
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