Force of a Punch to exceed the Max Static Friction Force

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Discussion Overview

The discussion centers around the mechanics of a boxer's punch in relation to static friction, particularly why boxers can absorb punches without losing their footing despite the high force exerted. It explores concepts of force, friction, inertia, and the duration of force application.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note that the average force of a boxer's punch ranges from 500-750 lb and question how this relates to the maximum static friction force between rubber shoes and concrete, which has a coefficient of static friction of 0.85.
  • It is suggested that a boxer's stance may increase the normal force, contributing to their ability to remain grounded when struck.
  • One participant proposes that the striking force may be less than the normal force when a boxer does not lose footing.
  • Another participant introduces the idea that a boxer's mass and inertia could play a significant role, especially in scenarios with low friction, such as standing on ice.
  • The time duration of the punch is highlighted as a critical factor, with the assertion that shorter force applications may rely more on inertia than friction.
  • There is a suggestion that momentum or energy transfer might be more relevant metrics than force alone when analyzing the impact of a punch.

Areas of Agreement / Disagreement

Participants express differing views on the factors influencing a boxer's ability to absorb punches without losing footing, with no consensus reached on the primary mechanics at play.

Contextual Notes

The discussion does not resolve the complexities of the interactions between force, friction, inertia, and time, nor does it clarify the specific conditions under which these factors operate.

h1a8
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I heard that the average professional boxer's force of punch is between 500-750lb.

If the coefficient of static friction of rubber (from shoes) to say concrete is at most 0.85 then why can boxers get hit (especially in the chest) without losing footing?

Does it have something to do with the stance to increase the normal force? Or is it that when the boxer does not lose footing, the striking force was LESS than the normal force?
 
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h1a8 said:
I heard that the average professional boxer's force of punch is between 500-750lb.

If the coefficient of static friction of rubber (from shoes) to say concrete is at most 0.85 then why can boxers get hit (especially in the chest) without losing footing?

Does it have something to do with the stance to increase the normal force? Or is it that when the boxer does not lose footing, the striking force was LESS than the normal force?
A boxer can lean in or be pushed back without having his feet move. The force of the punch is brief. The force from the floor can be longer lasting.
 
I would guess that the boxer's mass (intertia) must also play a role, and that a boxer standing on ice (say zero friction) could still deliver a significant fraction of that punch force.

The physical key is the time element. If the maximum force lasts only a very short time, then inertia plays a bigger role. For longer times, then friction plays a bigger role.

See if can find a plot of a boxing punch force versus time.

If you include the bio metrics, it becomes very complicated. http://boxingscience.co.uk/explosive-training-boxing/
 
No, one also needs to consider the duration or distance over which the force is applied - which also makes the force itself pretty meaningless.

Momentum or energy transfer would be more useful.
 

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