Isn't heat production a kind of work?

[Order]

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?

 

[LostConjugate]

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.

 

[russ_watters]

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.

 

[Order]

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.

 

[sardar]

Yes, heat production can be considered a type of work. In thermodynamics, work is defined as the transfer of energy from one system to another. When a living human is holding a heavy weight, no external work is being done because the weight is not being moved. However, the muscles in the human's body are still working and producing heat as a byproduct of their cellular processes. This heat production can be considered a type of work, as energy is being transferred from the body's cells to the surrounding environment. In this sense, a living human can be seen as a small power plant, converting chemical energy into heat energy. Power plants also do work by converting fuel into electricity, which is a form of energy. Therefore, it can be argued that there is a certain amount of work being done by the human body in the form of heat production.