Qualitative collisions questions

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Discussion Overview

The discussion revolves around qualitative aspects of collisions involving a larger sphere with a smaller sphere attached to its surface. Participants explore how changes in mass and velocity affect the likelihood of detachment upon impact with a surface, considering factors such as adhesion force and momentum transfer.

Discussion Character

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

Main Points Raised

  • One participant suggests that the likelihood of detachment depends on the mass of the smaller sphere and the deceleration of the larger sphere upon impact, proposing that if the force exceeds the adhesion force, detachment occurs.
  • Another participant expresses skepticism about detachment if the spheres are glued together.
  • A different participant explains that if the smaller sphere is attached to the back of the larger sphere, the force experienced by the smaller sphere increases with the mass of the larger sphere due to momentum transfer during impact.
  • A later reply questions whether the position of the smaller sphere (e.g., on the side versus the back) affects the qualitative detachment force, seeking clarification on how size differences influence this outcome.

Areas of Agreement / Disagreement

Participants have differing views on the likelihood of detachment, with some expressing skepticism about detachment under certain conditions while others provide reasoning based on momentum transfer. The discussion remains unresolved regarding the effects of different configurations and sizes on detachment likelihood.

Contextual Notes

Participants have not fully defined the parameters of adhesion force or the specific conditions under which detachment is considered, leaving some assumptions unaddressed.

goobertron
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Hello all. I have what seems to be a fairly simple problem but I need a bit of help on the reasoning and what happens in a qualitative sense if some factors change.

The problem is of e.g. a larger spherical type thing happily traveling along at a fixed velocity but with a smaller (e.g. 10x smaller by diameter) sphere adhered to the surface. This large/small pair now hits a surface.

What is the likelihood of detachment based on? I am thinking it is a function of the mass of the smaller particle and the deceleration of the combo pair as it hits the wall (i.e. if the F=ma in this scenario exceeds the adhesion force then the smaller thing detaches?)

Now, keep the smaller sphere the same size but increase the larger sphere (lets assume the same force of adhesion between the pair to keep it simple). If traveling at the same velocity as before it seems like there should be a greater chance of detachment, but is this because of momentum exchange? As you can see my Physics here is shocking!

If someone could sort out this basic issue first I'd then like to expand slightly.

Thanks!
 
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I doubt they'll detach if they're glued.
 
If I understand correctly, the smaller ball is attached to the back of the larger ball and the larger ball hits the wall. In this case, yes the smaller ball will feel a greater force upon impact the more massive the larger ball because of momentum transfer. You can do this experiment very easily. Hold a large exercise ball a few inches off the ground with a tennis ball resting on top and let go. When they both fall due to gravity and hit the ground, the tennis ball with go rocketing up into the air at a surprisingly high speed. This is a fun demonstration because the balls don't pick up much speed before they hit the ground, yet the tennis ball gains a great speed on impact. It demonstrates that total velocity is not conversed, only total momentum. When a high-mass, low-velocity object transfers its momentum to a low-mass object you get high velocity!
 
Thanks Chris - what about if it was stuck to the side? Does a larger or smaller parent ball give a more likely qualitative detachment force?
 

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