Can You Explain Why a Cork Won't Float in the Center of a Glass of Water?

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SUMMARY

The discussion centers on the phenomenon of a cork not floating in the center of a glass of water due to surface tension and the shape of the water's surface. Kathleen explains that the water's surface is higher at the edges of the glass, causing the cork to be buoyed towards the edge. Warren provides a practical solution to make the cork float in the center by overfilling the glass slightly, demonstrating that surface tension can be manipulated. This method effectively allows the cork to achieve a central position.

PREREQUISITES
  • Understanding of buoyancy and surface tension
  • Basic knowledge of fluid dynamics
  • Familiarity with experimental methods in physics
  • Awareness of the properties of water
NEXT STEPS
  • Research the principles of buoyancy and Archimedes' principle
  • Explore experiments demonstrating surface tension in liquids
  • Investigate the effects of water temperature on surface tension
  • Learn about fluid dynamics and the behavior of liquids in different containers
USEFUL FOR

Students, educators, and science enthusiasts interested in physics experiments and the principles of fluid mechanics will benefit from this discussion.

kath102245
Why is it that when you put a cork in a glass of water, it won't float in the center?
~Kathleen
 
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Because the water's surface is not flat. The water has surface tension, which tends to pull the water up along the edge of the glass. In other words, the water around the edge is higher than the water in the center. The cork seeks (via the buoyancy force) the highest position, which is at the edge.

- Warren
 
You can make the cork float on the center, though, if you're clever.

Fill a glass (with cork in it) to the brim with water. Slowly add water so the water goes slightly over the brim but does not spill. You'll find the cork now floats in the middle of the glass!
 
I just tried this with a cork - It works well.


Perhaps we should have a forum (or reference links?) of interesting experiments, along with an explanation of how they work. Between us all we must know hundreds of great, but simple, experiments. I suppose that this would be hard to arrange though...
 

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