Recent content by 1v1Dota2RightMeow

  1. 1

    Boundary conditions of a plane wave on a conductor

    Homework Statement Consider a plane monochromatic wave incident on a flat conducting surface. The incidence angle is ##θ##. The wave is polarized perpendicular to the plane of incidence. Find the radiation pressure (time-averaged force per unit area) exerted on the surface. Homework Equations...
  2. 1

    Help finding the vibrational frequencies and normal modes

    Oh gosh oh gosh - I just realized that I forgot to explicitly mention that there is a spring connecting the two particles. The scenario is that there is a double well potential with one particle in each well. The particles are connected to each other by a spring. We are considering small...
  3. 1

    Help finding the vibrational frequencies and normal modes

    Going in order of what you've written, this is my first question: are the equilibirum points the points where the potential of the wells is at a minimum? I found those to be at ##x=\pm \alpha##. But then again this does not include the spring potential...
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    Help finding the vibrational frequencies and normal modes

    Can I just completely throw out those constants that you've labeled "whatever"??
  5. 1

    Help finding the vibrational frequencies and normal modes

    But now I have absolutely no clue about how to decouple these equations. Linear algebra wasn't my best math course... hehe...
  6. 1

    Help finding the vibrational frequencies and normal modes

    Ok so then ##K=\begin{bmatrix}\frac{8\alpha^2\beta + k}{m} & -k/m\\-k/m & \frac{8\alpha^2\beta + k}{m}\end{bmatrix}##. I removed a negative sign from inside the matrix because it looks like you pulled it out to be in front of the ##K##.
  7. 1

    Help finding the vibrational frequencies and normal modes

    Ok so I found the coupled equations to be ##\ddot{x_1} =(\frac{-8\alpha^2 \beta -k}{m})x_1 + (\frac{-8\alpha^3 \beta + kx_2 -2k \alpha}{m}) ## ##\ddot{x_2} =(\frac{-8\alpha^2 \beta -k}{m})x_2 +( \frac{8\alpha^3 \beta + kx_1 +2k \alpha}{m}) ##
  8. 1

    Help finding the vibrational frequencies and normal modes

    Yup, in the Lagrangian I reduced using Taylor series.
  9. 1

    Help finding the vibrational frequencies and normal modes

    Homework Statement Let's say that I have a potential ##U(x) = \beta (x^2-\alpha ^2)^2## with minima at ##x=\pm \alpha##. I need to find the normal modes and vibrational frequencies. How do I do this? Homework Equations ##U(x) = \beta (x^2-\alpha ^2)^2## ##F=-kx=-m\omega ^2 x## ##\omega =...
  10. 1

    Wavefunction in a delta potential well

    I expanded it out to this, but nothing cancels nicely. ##\psi (x) = \frac{A(sin(kx)sin(ka)-cos(kx)cos(ka))}{sin(ka)}+\frac{B((1/2)(sin(kx)cos(ka)+cos(kx)sin(ka)-sin(kx-ka)))}{sin(ka)}## Should I have gone a different route?
  11. 1

    Wavefunction in a delta potential well

    I see 3 ways to do something with what you've suggested. Here is one attempt: ##\psi(x) = \frac{Asin(kx)sin(ka)+Bcos(kx)sin(ka)}{sin(ka)}## ##=Asin(kx) + \frac{B[(1/2)(sin(ka+kx)+sin(ka-kx))]}{sin(ka)}## ##=Asin(kx)+\frac{A}{2(e^{iKa}-cos(ka))}[sin(ka+kx)+sin(ka-kx)]##...
  12. 1

    Wavefunction in a delta potential well

    Homework Statement Using the equations given, show that the wave function for a particle in the periodic delta function potential can be written in the form ##\psi (x) = C[\sin(kx) + e^{-iKa}\sin k(a-x)], \quad 0 \leq x \leq a## Homework Equations Given equations: ##\psi (x) =A\sin(kx) +...
  13. 1

    Lagrangian of 2 rotating masses on a spring, sliding down plane

    What, this confuses me greatly. They slide down the plane, of course, but their potential energy comes from how far up the plane they are, no? Which would correspond to the height from the bottom (assuming there is a bottom).
  14. 1

    Lagrangian of 2 rotating masses on a spring, sliding down plane

    Ok so then ##PE=m_1gr_{1,z}+m_2g r_{2,z}## ? I changed to ##r## because I just realized that the masses have 3 coordinates. But I don't really understand how to transform to CoM separation coordinates.
  15. 1

    Lagrangian of 2 rotating masses on a spring, sliding down plane

    Homework Statement I am given the following scenario: 2 masses are connected by a spring and are on a frictionless inclined plane. They are free to rotate, oscillate, and slide down the plane. For the potential energy of the center of mass of the system, it is ##Mgh=(m_1+m_2)gh##. But isn't...
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