Can Falling From a Chair and a Building Cause Different Levels of Injury?

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Discussion Overview

The discussion revolves around the differences in injury levels resulting from falls from varying heights, specifically comparing falls from a chair to falls from a building. Participants explore the physics of falling, focusing on concepts such as force, deceleration, and kinetic energy.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes that while falling from a chair typically does not result in injury, falling from a building can be fatal, questioning how the same force applies in both scenarios.
  • Another participant emphasizes that the injury results from the deceleration experienced upon stopping, suggesting that greater speeds lead to greater deceleration and thus more severe injuries.
  • A participant reiterates the idea that the injury is related to the stopping force due to deceleration, and asks how to determine the time taken to decelerate from an initial velocity to zero.
  • In response, it is mentioned that calculating stopping time is complex and depends on various factors, including ground softness and body deformation limits. The participant suggests that considering kinetic energy may be more relevant, as higher kinetic energy results in more energy being dissipated upon impact.

Areas of Agreement / Disagreement

Participants express differing views on the factors contributing to injury severity, with no consensus reached on a definitive explanation. The discussion remains open to various interpretations of the physics involved.

Contextual Notes

Participants acknowledge that the stopping time can vary based on multiple factors, and there is no straightforward method to calculate it without considering specific conditions.

Phys_Boi
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If you fall off of a chair you don't get hurt, however, if you fall off of a building you die. How is this possible if you are experiencing the same force..
F=mg
 
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As the old joke goes, it is not falling down that hurts, it when you stop falling!

The force that will hurt you is the one due to the deceleration, (negative acceleration) when you suddenly stop. The faster you were going, the greater the deceleration.
 
DrClaude said:
As the old joke goes, it is not falling down that hurts, it when you stop falling!

The force that will hurt you is the one due to the deceleration, (negative acceleration) when you suddenly stop. The faster you were going, the greater the deceleration.
Okay! So how do you know the time from the initial velocity and 0 velocity?
 
Phys_Boi said:
Okay! So how do you know the time from the initial velocity and 0 velocity?
There is no easy way to calculate that. It depends on so many things, like the softness of the ground and how much deformation you can sustain before breaking. But generally speaking, you can consider that the stopping time is about the same in all cases, and therefore that the higher the velocity, the stronger the force.

It is probably more relevant to consider it from the point of view of kinetic energy rather than force. The more kinetic energy you have, the more will have get dissipated quickly when you hit the ground, so the more of that energy will go into squashing you and breaking your bones.
 
Okay! Thanks!
 

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