Optimal Compression for Soccer Balls: Official Circumference and Pressure

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Discussion Overview

The discussion revolves around the optimal compression of a soccer ball when placed between two objects, focusing on balancing safety and maximizing friction. Participants reference the official circumference of 70 cm and an inflation pressure of 13.5 psi, exploring theoretical and practical implications of these parameters.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the optimal compression of a soccer ball to ensure safety while maximizing friction between the ball and two objects.
  • Another participant suggests that maximizing friction requires maximizing the force between the surfaces, noting that the safe pressure for the soccer ball is uncertain and should be considered a limiting factor.
  • A hypothetical scenario is presented where the soccer ball is modeled as a cube, leading to a rough estimate of pressure during compression, although the participant cautions against using these calculations for experiments due to potential dangers.
  • A participant emphasizes the distinction between the inflation pressure of 13.5 psi and the burst pressure, arguing that understanding the burst pressure is critical for safe compression.
  • There is speculation about whether soccer ball manufacturers conduct burst tests for safety, with one participant expressing uncertainty about the motivations behind such tests.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the safe burst pressure of soccer balls and the implications of compression, indicating that multiple competing views remain without a consensus on the optimal approach or parameters.

Contextual Notes

Limitations include the lack of specific data on the burst pressure of soccer balls and the assumptions made in modeling the ball's shape and behavior under compression.

Blades0fChaos
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How much should a soccer ball be compressed between 2 objects for it to be safe for the soccer ball but also to maximize the friction between the ball and the objects. The values used for this should be the official circumference of 70 cm and a pressure of 13.5 psi.
 
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Well, static friction is modeled as proportional to the force between the two surfaces involved. So to maximise friction you need to maximise the force.

Your 'safe for the soccerball' is probably going to be your limiting factor. I really have very little idea how much pressure a football can withstand. But as a tyre has about 30 psi and makes a pretty big noise if they burst I'd say you probably don't want to go above that.

I going to make some further assumptions to get a rough estimate, I wouldn't recommend basing any experiments on these calculations as they could be dangerous.

Assuming the football is a cube, and keeps a constant cross-section (isn't physics great). Compressing it so it's 2/3 it's diameter in the compression direction would reach 27 psi. The 2/3 arises because the pressure you're referring to is pressure with reference to atmospheric, rather than absolute pressure.
 
That helps a lot thanks.

Does anyone know of someone doing an experiment much like this?
 
No, but the critical thing here is the pressure. 13.5 psi is the inflation pressure of the ball, but it isn't the pressure that it can safely withstand (burst pressure). If it were the burst pressure, it would burst the first time someone kicked it. So what you really need to know is the burst pressure. Then when you compress it between two plates, you use geometry to find the new volume and pressure of the ball when a certain force is applied. That's not a simple geometry problem, but it is doable.
 
There's a small chance that a football manufacturer has to do a bursting test for some safety reason...other than that I can't really think why anyone would want to do it!
 

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