Recent content by Uku

  1. U

    How to Treat ω in the Legendre Transform of a Lagrangian?

    Homework Statement I am given a Lagrangian, which, per assignment text, describes a single degree of freedom: L= \frac{I}{2}(\dot{q}+\omega)^2-kq^2 I need to find the Hamiltonian. Now, what I am wondering, when performing the Legrende transform...
  2. U

    Mathcad: differentiating with indexes

    Hello! The picture says a thousand words: http://www.hot.ee/jaaniussikesed/v6rrand.jpg In the last member under the square root, there is the error. For some reason I am not able to differentiate with an array index, ts1 is a single column 5 row matrix. How to solve this? The error says...
  3. U

    Why Are There Three Terms in the Differential Expression?

    HallsofIvy nailed it, thanks! U.
  4. U

    Why Are There Three Terms in the Differential Expression?

    Hello! I have this thermodynamical expression: dS=\sigma T^3 dV+4V\sigma T^2 dT+\frac{1}{3}\sigma T^3 dV=d(\frac{4}{3}\sigma T^3 V) Basically saying: \frac{4}{3}\sigma T^3 V=S Now, I do not get this.. d(expr) part, why are there three members to d(expr), with 2x dV and 1x dT.. nope...
  5. U

    Mass of used hydrogen in an isothermal process

    I messed up on R, since I wrote R=8.314*10^{-3}\frac{kJ}{K} when trying to write R in terms of kJ.
  6. U

    Mass of used hydrogen in an isothermal process

    Well the pressure differential is 0.4 MPa..
  7. U

    Mass of used hydrogen in an isothermal process

    By "could have" you mean you put in the numbers and got a different answer?
  8. U

    Mass of used hydrogen in an isothermal process

    Homework Statement I have hydrogen in a 12 L tank, at T=15 C. Some of it is used, the T = const. and Δp=0.4 MPa, the molar mass of hydrogen is M=2*10^-3 J/(mol*K). Find the mass of the used hydrogen. Homework Equations Am I wrong in simply using: \Delta m=\frac{M}{RT}V\Delta p ...
  9. U

    Problem with finding the complementary solution of ODE

    Okay, that is true, thank you. I now read from his example that the set is given by default. Still: how would you arrive at y_{1} and y_{2}? U.
  10. U

    Problem with finding the complementary solution of ODE

    Hello! On Pauls notes webpage, there is the following problem to be solved by variation of parameters: ty''-(t+1)y'+y=t^2 (1) On the page, the fundamental set of solutions if formed on the basis of the complementary solution. The set is: y_{1}(t)=e^t and y_{2}(t)=t+1 Now, I must be...
  11. U

    Method of undetermined coefficients, when to raise the guess

    Hello! I have some examples of non-homogeneous ODEs to be solved by the undetermined coefficients method. Two from "Pauls math notes" page: y''+8y'+16y=e^{-4t}+(t^2+5)e^{-4t} The compsol. for this is: Y_{c}=C_{1}e^{-4t}+C_{2}te^{-4t} The first guess for a particular solution would be...
  12. U

    MATLAB Regulate Grid Transparency in Matlab - Uku

    I need to fade the grid since I have to make a grayscale plot, the grid is very intrusive. Will layering achieve this effect?
  13. U

    MATLAB Regulate Grid Transparency in Matlab - Uku

    Hello! Is there a way to regulate grid transparency in matlab? Thanks, Uku
  14. U

    Laplace equation derivation, where does the potential go

    I think I mixed up, the potentials subtract. Thanks!
Back
Top