Work

[Brynn 2F]

Is there a guide or set of rules to remind us of when work will be positive vs. negative? Having some difficulty keeping the concepts straight.

[Jessica Cornelia Hongarta 1G]

If work is done by the system, then the value of work will be negative since the system is losing energy.
If work is done on the system, then the value of work will be positive since the system is gaining energy.

Hope this helps!

[Andrew Nguyen 1E]

Hi,

If it says that work is "done by" or "comes from" the system, then the system does work - thus losing it (negative w).
If it says that work is "done on" or "goes to" the system, then the system receives work - thus gaining it (positive w).

[Alex_Lee_1K]

To add on to the ideas above.

When something is expanding, such as pushing up on a piston, the work done BY the system is going to be positive, thus the work on the system will be negative
When something is being compressed, such as pushing the piston down on the outside, the work done BY the system is going to be negative, thus the work on the system will be positive.

[Melody_Tapia_1J]

When the system uses its internal energy to do work which causes its internal energy to decrease, the work is negative.

When the system gains internal energy then work will be positive.

[Sidharth Paparaju 3B]

When work is done BY a system, it is negative (the system loses energy) and when work is done TO a system, it is positive (the system gains energy).

[Bela Patel 2B]

When work is done BY the system, it is losing energy and the value will therefore be negative. When the work is being done ON the system, it is gaining energy and the value therefore will be positive.

[Kaitlyn Bateman 1L]

If the work is being done by the system, then work would be negative because it is losing energy by exerting it on the surroundings. However, if there is work doing done TO the system, then w would be positive because it is gaining energy from the surroundings.