Notation for Work Done: Mechanics vs. Thermodynamics

AI Thread Summary
In mechanics, work is denoted as "W" and represents the work done by the system on the surroundings, while in thermodynamics, work is defined in the opposite manner. Despite the different conventions, both fields ultimately measure work in Joules, emphasizing the importance of understanding the context to maintain correct sign conventions. The distinction in definitions does not inherently lead to mathematical errors if one is consistent in their approach. It's crucial to grasp the underlying principles rather than strictly adhere to specific notations. Overall, clarity in understanding the problem is key to correctly applying concepts from both mechanics and thermodynamics.
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My mechanics lecturer uses W for work done. My thermodynamics lecturer uses \Delta\xWhen asked about this, I have been told that W actually refers to energy. I am not sure whom to believe.

Also, in mechanics W is the work done by the system on the surroundings. In thermodynamics, work is defined the other way round. Why is that so? Won't that lead to mathematical errors when we use concepts from both branches to solve problems?

Thanks in advance for any help!
 
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It's true that work is energy. Whether you represent it with "W" or a "Q" or a "\zeta" or a ":-p" or whatever, you measure it in Joules (or some other unit of energy). As far as work being defined as "on the system, by the surroundings" or the reverse, it doesn't really matter. You just have to understand what's going on in the problem to get your signs right. If I lift a boulder to the top of a hill, I have lost chemical energy, and the boulder has gained an equal amount of potential energy. I have done x joules of work on the boulder. Or, if you want, the boulder has done -x joules of work on me. You can use it however you like, so long as you're consistent. Sometimes, teachers make definitions more specific than they need to be, for simplicity's sake. Like always putting the x-axis in the direction of motion and the y-axis along the normal force. You don't have to do that.
Just think your signs through. If you're asked to find the work done on a gas when a piston pushes in, you should have a positive answer, etc.
 
Nice ":-p" Archosaur...

:wink:
 

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