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zenterix

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- TL;DR Summary
- I saw the following quote in a thermodynamics book:

"The fundamental property in thermodynamics is work: work is done to achieve motion against an opposing force"

I'd like to know if this is accurate.

Is the following quote accurate:

"The fundamental property in thermodynamics is work: work is done to achieve motion against an opposing force"

Specifically, I am asking about the portion after the colon. I am a little confused by the notion of an opposing force.

Let's say we are in outer space and there is an object of mass ##m##. If we apply a force ##f## to this object it will accelerate, it will be displaced, and as far as I know, by definition we will be doing work. Of course, when we apply the force, there is a third law force in the opposite direction acting on us.

Similarly, if we have two charged particles, they each exert a force on the other of same magnitude and opposing directions. Thus, if we have particle A and particle B, particle A does work on particle B, and vice versa. Particle A is exerting a force and achieves motion in B. However, I don't see how this work is "against an opposing force" in an intuitive way. Sure there is an opposing force, but even in the absence of his opposing force, A would be doing work on B (because it would be exerting a force and there would be displacement of B).

Thus, I am confused that the definition of work used above is based on an opposing force.

"The fundamental property in thermodynamics is work: work is done to achieve motion against an opposing force"

Specifically, I am asking about the portion after the colon. I am a little confused by the notion of an opposing force.

Let's say we are in outer space and there is an object of mass ##m##. If we apply a force ##f## to this object it will accelerate, it will be displaced, and as far as I know, by definition we will be doing work. Of course, when we apply the force, there is a third law force in the opposite direction acting on us.

Similarly, if we have two charged particles, they each exert a force on the other of same magnitude and opposing directions. Thus, if we have particle A and particle B, particle A does work on particle B, and vice versa. Particle A is exerting a force and achieves motion in B. However, I don't see how this work is "against an opposing force" in an intuitive way. Sure there is an opposing force, but even in the absence of his opposing force, A would be doing work on B (because it would be exerting a force and there would be displacement of B).

Thus, I am confused that the definition of work used above is based on an opposing force.