Why Does a Hard Boiled Egg Spin and Raw Egg Won't?

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Discussion Overview

The discussion revolves around the physical behavior of hard boiled and raw eggs when spun on a flat surface, exploring the underlying mechanics of torque, angular momentum, and the internal dynamics of the egg's contents.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant notes that when spinning a raw egg, the torque is not transmitted to the liquid inside, drawing a parallel to spinning a glass of water with tea leaves.
  • Another participant questions whether the inability of the raw egg to spin is due to an imbalance of torque between the outside and the inside.
  • A different viewpoint suggests that the torque is transmitted slowly to the liquid inside a raw egg, and that the egg requires multiple spins for the yolk to gain enough speed to spin like a cooked egg.
  • It is mentioned that a method to determine if an egg is cooked involves spinning it and observing the behavior of the yolk when the shell is stopped.

Areas of Agreement / Disagreement

Participants present multiple viewpoints regarding the mechanics of spinning eggs, with no consensus reached on the exact reasons behind the observed behaviors.

Contextual Notes

The discussion includes assumptions about the transmission of torque and the dynamics of the egg's contents, which may depend on specific conditions not fully explored.

Tricks67
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why would a hard boiled egg spin and raw egg won't if made to spin on a flat surface?
 
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When you spin the shell of a raw egg, the torque is not transmitted to the liquid inside.
You can see this by rotating a glass of water with tea leaves. The leaves take a long time to spin if you spin the flass.
 
the torque is not transferred to the liquid..ok, then the reason it does not rotate is due to the imbalance of torque outside and inside?
 
For a raw egg the torque is transmitted slowly to the liquid inside. And since you usually spin an egg just once around, there is not much angular momentum that can be imparted to the egg so quickly. If you do keep on rotating it, after a few turns the yolk will pick up speed and the egg will go ahead and spin like a cooked egg.

Conversely, a standard method of determining whether an egg is cooked or not is to get it spinning and then suddenly bring it to a halt. Then release it. For an uncooked egg the yolk will not immediately stop, it will keep on going inside even after the shell is stopped. Then when you release the egg the spinning motion will resume.
 
thanks a lot!
 

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