Why Does Torque Point Perpendicular in Gyroscopic Precession?

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Discussion Overview

The discussion revolves around the phenomenon of gyroscopic precession, specifically addressing the nature of torque in relation to angular momentum and the direction it points. Participants explore the conventions of torque direction, the relationship between the wheel's spin and the applied forces, and the implications of these concepts in understanding gyroscopic behavior.

Discussion Character

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

Main Points Raised

  • Some participants question why the torque points perpendicular to the wheel and suggest that it may relate to the centripetal force direction.
  • One participant notes that the direction of the torque vector pointing toward the camera is a matter of convention, specifically referencing the "right hand rule." They argue that it could point in the opposite direction without changing the underlying physics.
  • Another participant proposes that the correlation between the wheel's counterclockwise spin and the torque direction is consistent, suggesting that the gravitational torque and the wheel's spin create a restoring torque that leads to precession.
  • There is a suggestion that the relationship between the wheel's spin and the torque direction is not merely a matter of convention but involves the interaction of multiple rotational vectors.

Areas of Agreement / Disagreement

Participants express differing views on the nature of torque direction and its implications for understanding gyroscopic precession. There is no consensus on the reasons behind the torque's direction or its relationship to centripetal forces, indicating ongoing debate and exploration of the topic.

Contextual Notes

Participants reference conventions and assumptions in their explanations, such as the "right hand rule," but do not fully resolve the implications of these conventions on the understanding of torque and precession. The discussion also highlights the complexity of the interactions between forces and rotational motion.

Who May Find This Useful

This discussion may be of interest to individuals studying physics, particularly those focused on mechanics, rotational dynamics, and gyroscopic systems.

Lego Science
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Veritasium posted a video on his YouTube channel called "Gyroscopic Precession." () In the video he explained how spinning the wheel caused the torque tho point toward "the camera" at 90° to the angular momentum. My first question is how and why does the torque point perpendicular to the wheel. My second question is why the torque force points to "the camera" and not the opposite direction, to me it seems like either direction would be kind of the some to the wheel. Please elaborate.
 
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The torque is a rotation about an axis and the axis is perpendicular to the wheel.

The reason the torque vector points to the camera and not the opposite direction is pure convention. It could easily be the other direction as well and nothing would change as long as you are consistent throughout with whatever convention you pick. In this case he used the well established convention of the "right hand rule".
 
Thank you paosiello2. As I have done more reading I have thought that maybe the reason the torque points toward the camera is because the wheel is spun around the rope holding the wheel, and the torque favors the centripetal force direction? I also have another question: The wheel spun counter clockwise (from the front) and the wheel spun around the rope counter clockwise, is this always a direct correlation?
 
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Lego Science said:
Thank you paosiello2. As I have done more reading I have thought that maybe the reason the torque points toward the camera is because the wheel is spun around the rope holding the wheel, and the torque favors the centripetal force direction?

No, it is only a convention. It could easily point away from the camera as well. As long as you suddenly don't change the convention you adopted from the start then you will always end up with the same answer.

The centripetal force direction is not really the issue. It's more the fact that you have a rotation vector of the wheel being added to the rotation vector of gravity acting on the wheel.

Lego Science said:
I also have another question: The wheel spun counter clockwise (from the front) and the wheel spun around the rope counter clockwise, is this always a direct correlation?
Yes, there is always a correlation. Here is my understanding of what is going on:

Gravity creates a torque about one axis. As the wheel starts to swing down caused by this gravitational torque, the spin of the wheel creates a restoring torque that momentarily also causes a slight rotation about the axis of the rope. As long as this gravitational torque acts on the spinning wheel then their will be this rotation about the axis of the rope. This rotation is technically called a precession.
 

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