|MadSci Network: Physics|
Eva, you have asked a very good question. Iím sorry I have not gotten back to you sooner. This strange phenomenon has plagued Cheerios eaters for centuries. The first thing we have to consider is the milk is not completely still. The scientific reasons for the Cheerios finding each other and sticking together are the small currents in the milk and adhesive forces. Surface tension plays a part in this too. Surface tension is a property which enable a needle to float on water and a water strider (we called them water skimmers) to float on the water. Surface tension also comes into play when washing clothes. The soap decreases the surface tension, which lets the soap between the fibers and remove the dirt. I have read where a duck canít float on soapy water because the soap has decreased the surface tension. I have not verified this because my wife wonít let me put a duck in her washing machine, honestly Iíve tried. What does this have to do with my Cheerios you ask? Well surface tension is one reason they float. Now, adhesive forces what are these? In a laboratory, you can measure liquids in a glass graduated cylinder. A graduated cylinder is a glass tube maybe 10Ē tall and a quarter inch in diameter (there are different sizes). If you put milk into the graduated cylinder and look at the level you should see the milk curve upward near the walls of the glass and is lower in the middle. This is adhesive forces which means the milk stick to the side of the bowl to a small extent, and to the Cheerios. The surface tension and attractions between other milk molecules pull it down in the middle. Ok so the real reason your Cheerios behave so strangely is because: 1. The currents in the milk make them move around, 2. Surface tension makes them float along with density, 3. The milk sticks to the sides of the bowl (adhesive forces) and to the Cheerios, which makes the other Cheerios stick to each other, and also stick to the side of the bowl. Eva keep up the great thinking. Now all of this has made me hungry, Iím going to get some Cheerios.
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