Is Mutual Ball Friction Causing Unexpected Ball Movement on a Tilted Plane?

  • Context: Undergrad 
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Discussion Overview

The discussion centers on the unexpected movement of balls on a tilted plane, particularly why some balls may move differently than anticipated when the plane is tilted. Participants explore concepts related to friction, pressure, and interactions between the balls, with a focus on theoretical explanations and analogies.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions whether the unexpected movement of balls is related to a "lubrication effect" or a local pressure spike affecting individual balls.
  • Another participant introduces the term "stickiness" but does not clarify its relevance to the observed phenomenon.
  • A participant expresses confusion about the concept of stickiness in the context of balls moving together and one ball popping out unexpectedly.
  • One participant suggests that the irregularities of the surface and the interactions between balls contribute to the unexpected movement, proposing that surface imperfections cause one ball to jump when impacted by others.
  • Another participant describes a mechanism where friction between balls leads to a trailing ball climbing rapidly when it rolls into a leading ball, drawing an analogy to tire interactions in racing, asserting that this is not related to lubrication.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the terminology or mechanisms involved. There are competing views regarding the role of stickiness, lubrication, and the effects of surface imperfections on ball movement.

Contextual Notes

Some assumptions about the surface conditions and the nature of ball interactions remain unaddressed, and the discussion does not resolve the definitions or implications of terms like "stickiness" or "lubrication effect."

y2j_molino
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When you have a bed of balls and you tilt the plane on whichh these bals are located, sometimes you don't get them all moving like a bed as you expect. Sometimes some balls pop. Is this call the lubrication effect? is it due to some local pressure spike focusing on solely 1 ball? thank you very much
 
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It's called "stickiness".
 
stickiness? sorry I don't get. If the balls are moving like a bed (they rotate), and suddenly one pops (only happens when the plane below them is moving), is this stickiness?
 
Thank you very much for your reply Naty1, but still I don't get it.
 
I suppose that Naty1 was kidding, I never heard of lubricant effect, so I can be wrong but I believe that you are not using some absolutely flat surface and that the balls hit each other all the time. Since all balls are moving and having some movement in it's axis when one ball pass in one little surface imperfection it jumps a little, when it comes in contact with the others balls the rotational movement of the others balls hit that one and kick it up.
 
If there is a some friction between balls, when a trailing ball rolls into a leading ball, the mutual rotation of both balls, plus the ball against ball friction causes the trailing ball to rapidly climb, almost straight up.

I'm familiar with this phenomenon from open wheel racing when I was young and daring, only the tire to tire friction is on the order of 1. When tire touched tire, the trailing car jumped into the air. I think the same mechanism is happening with these rolling balls.

This has nothing to do with lubrication.
 
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