Timeline for Is the work done on a system always equal to the negative of that work done by the surroundings?
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
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| Mar 28, 2021 at 18:54 | comment | added | Bob D | Yes, I agree for the piston example or for that matter any example where work is done it follows from N3. | |
| Mar 28, 2021 at 18:51 | comment | added | Chet Miller | @Bob D In my mind, for the piston example, It follows from N3. | |
| Mar 28, 2021 at 18:45 | comment | added | Bob D | I'm speaking of static friction, so there is no relative displacement. In my example no work is done regardless of the frame of reference. My only point (and perhaps you don't agree) is hat equal and opposite work does not necessarily follow from N3, unless I suppose we can say equal and opposite zero work. And of course the work done by the gas on the piston is equal to the work done by the piston on the gas. But that necessarily follows from conservation of energy. | |
| Mar 28, 2021 at 18:39 | comment | added | Chet Miller | @Bob D So the work is zero for both. But, with friction, if there is relative displacement, the work by each does depend on the frame of reference of the observer. This is a special case. I always imagine it as being observed by an observer moving with the average of the two boundary velocities so the amounts of work are equal. Anyway, for work done by or on a piston, the work done by the gas on the piston is equal to the work done by the piston on the gas. | |
| Mar 28, 2021 at 18:18 | comment | added | Bob D | Hi Chet. Re OPs Q1, I think it depends on what is meant by "restatement". If I exert a force F on you, you exert an equal and opposite force F on me per N3. But if maximum static friction force between each our feet and the ground is not exceeded, neither of us moves and no work is done on the other. | |
| Mar 28, 2021 at 3:49 | history | answered | Chet Miller | CC BY-SA 4.0 |