Negative vs. positive work

[Julia Mizzi 2I]

When do we know if work is negative or positive?

[Rohan Ghosh Choudhuri]

In general, we look at it from the perspective of the system we are looking at. So, if work is being done on the system, we use a positive work value and if the system is doing the work, we use a negative work value. It's helpful to use the example of the system pushing out the volume (doing work on the system), because we know that the system is losing energy when this happens (negative work).

[Mark Torres 2I]

You can also think of it as energy entering a system making work positive, while energy exiting a system makes work negative.

[Sabrina_Huang_1K]

When trying to figure out whether positive or negative work is being done on a system is by figuring out what the system is. Once you have figured out the system, if work is being done on the said system then the work value is positive. The opposite goes for if the system is doing the work then the work value is negative. An example of this would be the piston-cylinder example we learned about in class. If we were to push down the piston we would be decreasing the volume and increasing the pressure, but overall we are doing work on the system. On the other hand, if the gas inside the piston were to expand, we would say the that the system is doing work on the surroundings.

[805810326]

Its best to consider work from a physics perspective. Work is force times distance and when analyzing a system, if it is doing work then this means the work is usually negative however if we affecting a system ie pushing a piston we are doing positive work or energy into the system.

[eriko vong 3D]

Positive work is when the work is done to the system (energy is going in), and negative is when the system is doing work (energy is going out into the surroundings).

[Sunny Do 1G]

Work is positive when there is work being done on the system. In other words, energy is being absorbed into the system. Work is negative when the system itself does work or releases energy.

[MelodyJiang]

Work is negative when the system is doing work itself, but when work is being done on the system, work is positive.

[Jessica Norman 1B]

Work is negative when the system is doing work (i.e. when a gas expands on a system), work will be positive when work is being done on a system.

[Rubani Chugh 2K]

We know work is negative when the system has done work. On the other hand, work is positive when work has been done on the system by the surroundings. For example, a system has done work when there is an increase in volume due to expansion. Work has been done on the system by the surroundings when there is a decrease in volume due to compression.

[205670593 1I]

Work is negative when the system is doing work. An example of this would be when the system volume expands against a force. Positive work is when work is done on the system, an example being when the system volume shrinks/contracts.

[Michelle Lim 2G]

Work being done to the system is positive work when energy is going in, and negative work is when the system is doing work when energy is going out into surroundings.

[Sydney Tanimitsu 2B]

Negative work is when the system is doing work and positive work is when work is being done on the system.