Physics degrees of freedom problem

AI Thread Summary
The discussion revolves around calculating work and heat transfer for a 1.12 mol sample of an ideal diatomic gas undergoing a process with changing pressure and temperature. Participants express confusion over how to find work or heat (q) when neither pressure, volume, nor temperature are constant. The connection between degrees of freedom and heat capacity is highlighted as crucial for understanding the system's energy changes. Additionally, the linear relationship between pressure and temperature is noted as a potential avenue for analysis, suggesting that graphing pressure versus volume could help determine work done. Overall, the challenge lies in integrating these concepts to derive the necessary thermodynamic quantities.
squib
Messages
39
Reaction score
0
A 1.12 mol sample of an ideal diatomic gas at a pressure of 1.00 atm and temperature of 491 K undergoes a process in which its pressure increases linearly with temperature. The final temperature and pressure are 735 K and 1.39 atm. Assume 5 active degrees of freedom.


Neither pressure nor volume nor temp are constant, so I'm confused to how I'm supposed to find work or q.
 
Physics news on Phys.org
Have you seen this formula before?

\Delta Q = \Delta U \pm W, the \pm is there depending on how you define when is work positive. If I recall correctly U = \frac {q}{2} n R T where q is the numbers of degree of freedom.
 
squib said:
A 1.12 mol sample of an ideal diatomic gas at a pressure of 1.00 atm and temperature of 491 K undergoes a process in which its pressure increases linearly with temperature. The final temperature and pressure are 735 K and 1.39 atm. Assume 5 active degrees of freedom.


Neither pressure nor volume nor temp are constant, so I'm confused to how I'm supposed to find work or q.

A couple of things you need to key on. What is the connection between degrees of freedom and heat capacity? And what can you do with the fact that the P vs T curve is linear?
 
I assume I could graph P vs V and find work, but that seems like more work then should be neccesary. I can find the change in U, or overall energy of the system, the only problem I'm having is with work, which should give me heat since I know U.
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top