What Causes the Strange Sensation of a Spinning Motor's Force?

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Discussion Overview

The discussion revolves around the sensations experienced when holding a spinning motor, particularly focusing on the forces at play and the perceived changes in weight and directionality. Participants explore concepts related to rotational motion, momentum, and the physical effects of spinning objects.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant describes a personal experience with a spinning motor, noting a strange sensation and a feeling of changing weight, prompting a question about the underlying forces involved.
  • Another participant inquires whether the strange sensations occurred when the motor was held still or during attempts to move it, suggesting it might be a gyroscopic effect.
  • A participant clarifies that the object was not a gyroscope, indicating it was a spinning metal wheel with a single direction of rotation.
  • One response introduces the concept of angular momentum, suggesting that the resistance felt when trying to change the orientation of the spinning disc relates to the conservation of momentum and requires work to alter the system's state.
  • Another participant speculates that the perceived randomness in the direction of force could be due to the momentum of the spinning object interacting with the holder's hand, which may not be perfectly steady.

Areas of Agreement / Disagreement

Participants express varying interpretations of the sensations experienced with the spinning motor, with some suggesting gyroscopic effects while others propose explanations based on angular momentum. No consensus is reached on the exact nature of the forces involved.

Contextual Notes

Some assumptions about the nature of the spinning object and the forces at play remain unresolved, and the discussion does not clarify the specific definitions of terms like "moment of momentum." The relationship between the sensations and the physical properties of the spinning motor is not fully explored.

Who May Find This Useful

This discussion may be of interest to individuals exploring concepts in rotational dynamics, physics educators, and those curious about the physical sensations associated with spinning objects.

tommyburgey
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Ages ago in my physics classes my teacher would have a large metal motor that would spin very fast, it was attached to a metal board. When he asked people to hold it it felt really strange and would pull you in apparently random directions. When it didnt spin it was very heavy but when it was spinning it's weight felt as though it changed, but I can't imagine it weighing less on scales. He would always say that he wanted to know what the force was, does anybody know about it or have any links?
(sorry if this was a nooby question)
Thanks, Tom.
 
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Did it feel weird if you were holding it perfectly still or when you tried to move it in any way?

I can't really tell by your description, but it seems like you had a good sized gyroscope in your hands.
 
Both, I think. It wasn't a gyroscope though as there was only one direction of rotation (it was basically a spinning metal wheel).
 
This sounds very much like the moment of momentum, L, and the force you mentioned would probably be better described as a resistance towards the force you apply when trying to change the orientation of the disc. It is the same thing that makes bicycles more stable than you'd expect at first glance.

Every bit of the rotating disc is a moving mass and it thus carries a momentum. Collectively these momenta constitute the moment of momentum. Changing the orientation of the disc means chaning the movement of each bit, and thus the moment of momentum, which is conserved in an isolated system. This requires some work.
 
also, you holding the spinning whatever it was, your hand isn't perfectly steady, so the momentum of the spinning object would move your hand seemingly random because the direction it(the mometum) is moving keeps changing (not sure if its true, but it sounds right =) )
 

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