Gyroscope Precession: Understanding Angular Momentum & Energy

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    Gyroscope Precession
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Discussion Overview

The discussion revolves around the phenomenon of gyroscope precession, focusing on the underlying principles of angular momentum and energy. Participants explore the mechanics of precession, the source of vertical angular momentum, and the relationship between gravitational potential energy and the motion of the gyroscope.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant asserts that precession is caused by the torque due to gravity acting on the angular momentum vector, which is always perpendicular to the torque.
  • The same participant questions the origin of vertical angular momentum, noting that it was not present initially and that there is no torque in the vertical direction.
  • Concerns are raised about the energy associated with precession, with one participant suggesting it may relate to gravitational potential energy, though they find this unlikely given the horizontal motion of the gyroscope's center of mass.
  • Another participant introduces Euler's equations as a potential framework for analysis, stating that precession can occur without a torque if the system rotates about its principal axes.
  • This second participant also mentions that the Earth experiences precession without significant torques acting on it, referencing its free fall orbit.
  • A suggestion is made to consult a technical manual for further insights into gyroscopic principles.
  • A video resource is recommended for additional understanding of the topic.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of torque for precession and the source of vertical angular momentum. The discussion remains unresolved, with multiple competing perspectives on these aspects.

Contextual Notes

Some participants reference specific technical concepts, such as Euler's equations, but there is a lack of consensus on their application to the problem at hand. The discussion also highlights potential gaps in understanding regarding the relationship between gravitational forces and angular momentum.

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Hello. I know there are quite a few threads about this, but I couldn't find what I was looking for. This topic has been driving me crazy over the last couple of days. I know the cause behind the precession. It's because the torque due to gravity about the pivot tends to rotate the already present angular momentum vector since it is always perpendicular. This is only possible by rotating the wheel itself, thus causing the precession. What I don't understand is where the angular momentum in the vertical direction comes from, since it was not present initially. There is no torque in the vertical direction. And what about the energy due to precession? Is it because of some change in gravitational potential energy? This seems unlikely since the entire motion of the centre of mass of the disc is in the horizontal plane. Any help will save me from insanity.
 
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Find an old Sperry Gyroscope technical manual.
 
transparent said:
Hello. I know there are quite a few threads about this, but I couldn't find what I was looking for. This topic has been driving me crazy over the last couple of days. I know the cause behind the precession. It's because the torque due to gravity about the pivot tends to rotate the already present angular momentum vector since it is always perpendicular. This is only possible by rotating the wheel itself, thus causing the precession. What I don't understand is where the angular momentum in the vertical direction comes from, since it was not present initially. There is no torque in the vertical direction. And what about the energy due to precession? Is it because of some change in gravitational potential energy? This seems unlikely since the entire motion of the centre of mass of the disc is in the horizontal plane. Any help will save me from insanity.

This can be analyzed using the Euler's equations...which I haven't worked with in several years. However, I'd like to point out that there does not necessarily need to be a torque in order for precession to be present. In fact, since the force of gravity acts on the center of mass of the system, it does not, if I recall correctly, present a torque to the system if the system is rotating about its principle axes. The Earth, for example, is in free fall orbit and there are no torques really acting on it, and yet its rotation precesses once every ~10,000 years. There is also a nutation present.

Maybe look here for some more details:
http://en.wikipedia.org/wiki/Euler's_equations_(rigid_body_dynamics)
 
I'd suggest watching this video.

http://ocw.mit.edu/courses/physics/8-01-physics-i-classical-mechanics-fall-1999/video-lectures/lecture-24
 

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