Examples of work being done


Moderators: Chem_Mod, Chem_Admin

Angela 1K
Posts: 80
Joined: Fri Sep 29, 2017 7:05 am

Examples of work being done

Postby Angela 1K » Thu Jan 25, 2018 9:12 pm

What are some examples in which work is being done on a system?

In an example where volume and pressure both change, is work still being done on the system?

In a system that expands against a vacuum, is work being done?

Shawn Patel 1I
Posts: 54
Joined: Thu Jul 27, 2017 3:01 am

Re: Examples of work being done

Postby Shawn Patel 1I » Thu Jan 25, 2018 10:33 pm

Hey,
An example of a system doing work would be when a gas is pushing against a piston. When volume and pressure are changing, there can be work being done on the system. If there is a vacuum, work cannot be done because there is nothing to do work against.

Ammar Amjad 1L
Posts: 54
Joined: Thu Jul 27, 2017 3:00 am
Been upvoted: 1 time

Re: Examples of work being done

Postby Ammar Amjad 1L » Thu Jan 25, 2018 10:37 pm

Yes what Shawn said above is true. Just to add on, a system does no expansion work when it expands into a vacuum, because there is no opposing force. Expansion work against zero work is called free expansion.

Yu Chong 2H
Posts: 30
Joined: Fri Sep 29, 2017 7:05 am

Re: Examples of work being done

Postby Yu Chong 2H » Fri Jan 26, 2018 3:37 pm

I think that for the purpose of our class, we can think of work done by a system to be a force pushing against the system. If it's a gas, the work done on a system will most likely cause a contraction of the gas.

204932558
Posts: 23
Joined: Fri Sep 29, 2017 7:05 am

Re: Examples of work being done

Postby 204932558 » Sat Jan 27, 2018 12:09 pm

If gas expands against vacuum no work is being done because the external pressure is zero. An example of work done on a system would be a piston compressing the gas inside a column. Work is done on the gas.

Justin Folk 3I
Posts: 43
Joined: Wed Sep 21, 2016 2:56 pm

Re: Examples of work being done

Postby Justin Folk 3I » Sat Jan 27, 2018 8:33 pm

For example pushing a cart is work being done. You use some energy (instead of to heat up) to push the cart.

Oscar Valdovinos 1I
Posts: 29
Joined: Fri Sep 29, 2017 7:05 am

Re: Examples of work being done

Postby Oscar Valdovinos 1I » Sat Jan 27, 2018 11:45 pm

Another aspect of work to note is that work is not a state meaning that its value depends on the path taken. A quick example of this would be pushing a ball 100ft on a flat surface would require less work on the system than pushing that same ball uphill for a 100ft.

Jaewoo Jo 2L
Posts: 31
Joined: Fri Sep 29, 2017 7:06 am

Re: Examples of work being done

Postby Jaewoo Jo 2L » Sun Jan 28, 2018 12:35 am

since work is force x distance, doing anything that requires a certain force to move something a certain distance (like push-starting a car) is work being done.


Return to “Concepts & Calculations Using First Law of Thermodynamics”

Who is online

Users browsing this forum: No registered users and 2 guests