Isn't heat production a kind of work?

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SUMMARY

This discussion clarifies the distinction between work done on an object and the microscopic work performed by a human body when holding a heavy weight. While textbooks state that no work is done on the weight due to gravitational resistance, the act of maintaining muscle tension involves energy expenditure, resulting in work done on surrounding air molecules. The conversation emphasizes that although no output work is accomplished on the weight, significant input work occurs in stabilizing the body, leading to useful work in the form of heated air rising, thus fulfilling the definition of work.

PREREQUISITES
  • Understanding of basic physics concepts, particularly work and energy.
  • Familiarity with the definitions of force and motion.
  • Knowledge of thermodynamics, specifically heat transfer and energy conversion.
  • Awareness of muscle physiology and how muscles generate force.
NEXT STEPS
  • Explore the concept of work in physics, focusing on the work-energy theorem.
  • Study thermodynamics principles, particularly the laws of thermodynamics related to energy transfer.
  • Investigate muscle physiology and the mechanics of muscle contraction.
  • Learn about the principles of buoyancy and how heated air affects gravitational forces.
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in the nuances of work and energy in biological systems, particularly in understanding the complexities of physical exertion and thermodynamics.

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One often read in coursebooks that no work is done when (a living human is) holding a (heavy) weight. But is there not microscopic work done when you are standing there shaking like jelly. You have become a little power plant and power plants do work, don't they? There is a certain power, energy per time unit, and creating energy is work, isn't it?
 
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The textbooks are specific to work being done on the weight, not the air molecules around you. You are correct, work is being done on the air molecules because you are applying a force to them and they are moving.

In the case of the weight you are applying a force however it is not moving since gravity is working destructively against you, no work is accomplished.
 
It's a difference between input and output. It takes a lot of input work to hold your muscles steady, but you are doing no output work on the weight you are holding. You might say that in that situation, your body is 0% efficient.
 
Ok, so there is not only work done, but even useful work. Because air molecules of higher temperature will rise up and overcome gravitational potential. And therefore create a force times distance, which is work by definition. But there is no work done on the weight.

I wish the books could be more clear on this point. Thanks for replies.
 

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