Oh this is a must-try little experiment!
First, tell your bright students that if you put a piece of cork in the middle of a glass of water, it will not stay there. The cork will float off to the edge of the glass. (Smart cork. I would hurry to find the edge of the water, too….)
Your bright students won’t believe you, so spend a few minutes demonstrating.
Now, just before the bell rings, tell your bright students that they can go home as soon as they figure out how to keep that cork in the middle of the glass of water.
Er…well, wait a second. You want to go home soon, yes? This might take a while. Okay, assign it for homework and discuss in the next lesson.
Eh? You need the answer? Click or read below!
Fill the glass almost to its rim, and then place the cork in the water. Then, very carefully, pour a little more water into the glass until the water forms a convex shape just above the rim. The cork needs to seek the highest point (ask your science teacher why). It will naturally float uphill to the center of the glass.
Did you know that?