Why do gyroscopes not fall down?

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    Fall Gyroscopes
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Discussion Overview

The discussion revolves around the mechanics of gyroscopes, specifically addressing why they do not fall down when rotating. Participants explore concepts related to torque, forces, and the behavior of gyroscopes in both linear and rotational motion. The conversation includes technical explanations, conceptual clarifications, and challenges regarding the forces at play in a rotating gyroscope.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question the forces that prevent a gyroscope from falling, specifically asking what opposes gravity when the gyroscope is rotating.
  • Others argue that an upward force at the support exists, but this force alone does not prevent the gyroscope from falling when not rotating.
  • A participant requests a free body diagram to clarify the forces acting on a rotating gyroscope.
  • There is a discussion about the nature of torque, with some asserting that the torque from gravity is horizontal and does not create a downward torque that would cause the gyroscope to flip.
  • Some participants express confusion about the concept of a "righting moment" that counters gravity and prevents the gyroscope from flipping down.
  • One participant mentions that the precession of the gyroscope balances the torque due to gravity, but questions remain about whether uniform precession is the only motion a spinning body can undergo under torque.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the mechanics of why a gyroscope does not fall down. There are competing views on the nature of torque and the forces involved, leading to ongoing confusion and debate.

Contextual Notes

Participants express uncertainty about the definitions and implications of torque and forces in the context of gyroscopic motion. The discussion highlights the complexity of understanding the interactions between gravity, torque, and angular momentum.

  • #31
A.T. said:
Laithwaites misconceptions ...
I think there are a couple in that video. I only posted the video because of the large gyros. Near the start of the video, he demonstrates that apparent static friction is less for the smaller objects on a tilted surface, without a clear explanation (which is probably related to surface area versus mass, since the smaller objects are thinner vertically (I seem to recall something about a type of bonding that occurs between solid objects that adds to static friction effects)). Next he doesn't understand how transformers work with a pair of coils with the driving one on the bottom and the driven on placed on top.

As for the large gyro on the stand with the spring, the spring supported mount does not move upwards despite his claim that it does so when he speeds up the the rotation of the pole. However, the center of mass of the system does have an effect. When the center of mass is accelerated vertically, the spring supported mount will react accordingly. Also when he's grabbing the pole, he could be exerting a vertical force in addition to the horizontal force.

Near the end of the video, he demonstrates a "gyro" made up of a bunch of masses at the end of spokes. This demonstrates the 90 degree delay from torque to peak position lateral position of the masses (which is why the cyclic control on a helicopter is advanced by 90 degrees).
 
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  • #32
A.T. said:
An alternative is the explanation in the video below, which uses linear dynamics to explain it (e.g. force couple instead of torque):



If you like the above explanation, but want more detail on the internal transmission of the forces in the spinning rigid body, I recommend the below animation:

 
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