Go Back   Physics Help Forum > High School and Pre-University Physics Help > Thermodynamics and Fluid Mechanics

Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum

Reply
 
LinkBack Thread Tools Display Modes
Old Feb 26th 2018, 05:02 PM   #1
Junior Member
 
Join Date: Feb 2018
Location: Guatemala
Posts: 1
Stationary vertical cylinder with heavy piston

Hi,

I'm just starting to learn thermodynamics and I'm completely stuck with a problem:

A stationary vertical cylinder, closed at the top, contains a gas whose volume may be changed with the aid of a heavy, frictionless piston of weight w.
a) How much work is done by the external force in compressing the gas by an amount dV by raising the piston a distance dy?
b) If this device is used as part of an engine, what expression is appropriate to calculate the net work delivered to or received from the surroundings?
c) If this device is used only to produce temperature changes of the gas, what expression for work would be appropriate?


Ok, if I'm not wrong that would be classified as a typical hydrostatic system with thermodynamic coordinates P, V and T. And it should be a quasi-static process. Can I assume that the gas is an ideal gas and that the process would be isothermal? So that $\displaystyle W=\int_{V_{i}}^{V_{f}} P dV$?
Then, by getting a free body diagram, I could work out P?

For question b, I assume that it would have to be the net work done during a cycle. Which would be the combination of compression and expansion.

And for question c, I think it should be an isobaric process? So that the Volume and the temperature change but the pressure stays constant?

Are these assumptions and ideas correct and how could I formalize them to answer the questions properly?

Thanks a lot!
BobaJ is offline   Reply With Quote
Reply

  Physics Help Forum > High School and Pre-University Physics Help > Thermodynamics and Fluid Mechanics

Tags
cylinder, heavy, piston, stationary, vertical, work



Thread Tools
Display Modes


Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
Nitrogen in piston-cylinder help Munch Advanced Thermodynamics 0 May 16th 2016 10:36 PM
Piston-Cylinder System ayhn14 Thermodynamics and Fluid Mechanics 1 Mar 31st 2016 01:37 AM
Fluid flow across a cylinder kept an angle with vertical qwertynm7 Advanced Mechanics 2 Jul 28th 2015 12:38 PM
Piston-cylinder chevy900ss Thermodynamics and Fluid Mechanics 2 Feb 14th 2014 08:29 AM
Help calculating the energy transfer of a piston-cylinder assembly kawf Thermodynamics and Fluid Mechanics 2 Jan 27th 2010 05:31 AM


Facebook Twitter Google+ RSS Feed