1. L

    Changes of gas in a vessel with a tap

    "A vessel of volume 2.0*10^-2 m^3 contains an ideal gas at a pressure of 1.50*10^5 Pa. A tap attached to the vessel is opened and the gas expands adiabatically until its pressure equals the atmospheric pressure of 1.01*10^5 Pa. The tap is then closed. The gas is allowed to return to its original...
  2. F

    Expansion - Inflation - in an infinite Universe

    Inflation - expansion. Need an explanation - Last piece to explain logically past the breakdown of the math. My thinking is once I get the link clearly demonstrated that it Cycles BB - Gravity - BB - Gravity on larger scales then Math can be applied to whats we are all missing...
  3. Q

    Need help with Area Expansion Problem (Thermal Expansion)

    A steel ring with a hole having area of 3.990 cm2 is to be placed on an aluminum rod with crosssectional area of 4.000 cm2. Both rod and ring are initially at a temperature of 35.0°C. At what common temperature can the steel ring be slipped onto one end of the aluminum rod?
  4. F

    Thermal expansion and lattice constants

    Hi all, I'm not a physicist, but I need to calculate the lattice parameter of a cubic crystal in dependence of the temperature. The linear expansion coefficient in dependence of Temperature is given by the general formula: \alpha(T) = A+B*T+C*T^{2}+C*T^{3}+D*T^{4} where A,B, C, D are...
  5. L

    Modelling 2phased expansion valve

    Hello, I am currently trying to model a 2phased expansion valve in Simscape (matlab - simulink). They already have a Variable Local Restriction for a 2Phased model (https://nl.mathworks.com/help/physmod/simscape/ref/variablelocalrestriction2p.html) which I would like to use for my model...
  6. Z

    Heat absorption in reversible isothermal expansion

    2kgs (total mass) of steam goes through a revesible isothermal expansion at 500 degrees celcius. During the expansion the pressure drops from 300 kpa to 200 kpa What is the heat absorbed by the steam during this process? I guess that steam cannot be assumed to be ideal which makes the...
  7. Z

    Saturated mixture expansion thermodynamics

    A vessel is containing a saturated mixture of 1kg liquid water and 100g steam at 100 degrees celcius. The vessel is connected to another container with the exact same volume, and the mixture expands freely so it fills the doubled volume. The system is thermally isolated. What is the final...
  8. C

    Interaction between oblik shock wave and expansion wave

    In a monodimensional supersonic flow in canal with an angle of inclinason theta, we have an oblick shock wave up and expansion wave down, but do we have interaction between oblick shock and wave of expansion ?
  9. D

    Need assitance re: Internal energy calculations on Polytropic expansion

    Hi everyone, I'm having an issue with a question I'm trying to solve. Here is the question: A gas with an initial pressure of 800Kpa, 0.02m3 expands following a polytropic process. The final conditions are 350Kpa, 0.042m3. Find the following: a) Index of expansion b) Work done c)...
  10. L

    Loss due to contraction vs loss due to expansion

    I was told that the friction loss due to expansion is bigger than the friction loss due to contraction because of flow separation , is it true ? why ?
  11. L

    coefficient of volume expansion of ideal gas

    why the coefficient of volume expansion of ideal gas is given by the formula = 1/T ? by saying it = 1/T , the assume delV / V amd delP / P = constant ? why ? when the temp change , the density and specific volume(v) also change , right ?
  12. E

    Thermal expansion of a solid body

    Hello, I suddenly feel quite confused with the simple equation of a body length (1d case) after being exposed to a temperature difference : L_final=(1+alpha*dT)*L_initial while dT is the temperature difference I try to use this equation twice - 1. I want to find the length of a body...
  13. J

    Heating with thermal expansion

    If a cup of milk is heated from 30'C to 60'C with thermal expansion, is it correct to say the kinetic energy and potential energy of the molecules of milk both increase?
  14. kelsiu

    Why dU may not equals dW in free expansion?

    From a video lecture, it is mentioned that "dU≠dW in Joule's free expansion if the process is irreversible and adiabatic" Mentioned in around 36:00-38:00 in the video: https://www.youtube.com/watch?v=RrVq7Yduz2g What I would like to ask is why in this irreversible adiabatic process, dU≠dW? Is...
  15. A

    Joule-Thompson expansion

    imgur.com/zjrSOwu So I think for part 1, I can examine the internal energy change of gas passing through the valve, and then relate that to temperature. I'm a bit confused on how to proceed though. For part 2, I have no clue how to define the system to prove entropy always increases. Thanks!
  16. G

    Problem in adiabatic expansion and cooling

    Hey guys. I have a problem in adiabatic cooling and expansion and there is something I didn't understand. when we are compressing air without transfering heat(so adiabatically), why does the air heat? As I know, because of moving "wall". when molecules heat on moving wall kind of baseball bat...
  17. W

    Coefficient of linear expansion question

    Measurements of XRay scattering from an unidentified metal are made. The bragg peaks are θ = 50° and 46° for temperatures of 299K and 1250K respectively. Calculate the linear expansion coefficient of the metal. This is given by (1/L)(dL/dT) The rate of change isn't uniform, so the...
  18. Troll

    Mind expansion exercise

    If time/space was infinite and we could observe it as a whole, what would we observe?
  19. A

    Thermal expansion and anharmonicity

    (sorry for my english) Solid state physics books (for example Aschroft/Mermin) say that in a perfect harmonic crystal there isn't thermal expansion. On the other hand , they calculate grüneisen parameter and coefficient of thermal expansion for the Debye model (which is a purely harmonic...
  20. B

    thermo expansion

    http://s13.postimg.org/4opdl7bev/screenshot_83.png what should i do?