Try this experiment right away. First, boil an egg, then swing it vigorously on the table with your hand.
If you do it right, chances are you will see this strange phenomenon: when rotated, the egg gradually… stands up, rotates vertically, like what you see in the picture below. .
Did you see anything strange?
But what happened? In fact, this phenomenon has been documented for a long time, but science took a long time to study. In 2002, experts came up with a solution, but the answer was a series of extremely complex mathematical formulas.
Fortunately, physicists are now able to come up with a simpler solution.
“The strange phenomenon of egg rotation has baffled science for more than 100 years, but it has never been able to come up with a simple solution,” said Rod Cross, a researcher from the University of Sydney (Australia).
“Those solutions won’t help a college student, even a physics teacher.”
The problem is that for a long time we did not have the necessary measuring equipment. Science cannot separate the rotation and friction forces , causing the egg to gradually stand up.
But in the end, the answer is there. According to Cross, the phenomenon occurs because the egg rotates not only in one axis, but in two at the same time.
Place an egg horizontally on the table, you will see a slightly raised end. If you try to rotate it slightly, there will be a horizontal axis along the egg body and perpendicular to the table. It is called the short axis (or horizontal axis).
But the egg itself also rotates along a different axis located at the center of the fruit. And because of the special shape, the center of the egg and the place where the egg comes into contact with the iron does not coincide. As a result, when rotating, the egg will wobble. In physics, this is called “precession”.
The egg will rotate along the short axis, but gradually move to the long axis. That’s because the so-called precession on the axis is short, causing the axis to gradually change angle.
But after all, what makes the egg stand up is the force of friction . The long shaft will suffer precession from the friction force caused by the egg contacting the table surface, making the angle change process happen faster. As a result, the egg stands up.
According to Cross’s experiment, the precession of the two axes will be described by two completely separate equations. In addition, the experiment also determined that the faster the spin, the faster the egg stands. If the rotation is too slow, the frictional force generated will not be enough to create this phenomenon.
Finally, maybe here many people will wonder why boiled eggs? This is because raw eggs have a liquid core, and that makes the center of the egg unstable. The egg couldn’t even rotate for too long for that reason.
Results when trying to spin a raw egg.
The study was published in the European Journal of Physics.