Recent content by David Koufos

  1. David Koufos

    How do I know if my eigenvectors are right?

    Ok. I tried that and got the right diagonal matrix. Thank you. I mixed up ##CMC^{T}## with ##C^{T}MC##
  2. David Koufos

    How do I know if my eigenvectors are right?

    Ok I found the diagonal now. Thank you. I mixed up ##CMC^{T}## with ##C^{T}MC##
  3. David Koufos

    How do I know if my eigenvectors are right?

    Ok. I tried that and got the right diagonal matrix. Thank you. I mixed up ##CMC^{T}## with ##C^{T}MC##
  4. David Koufos

    How do I know if my eigenvectors are right?

    I just tried that with this specific example, and using my 2nd eigen vector ##(-1, 2)## I do indeed get that [M]u = λu. So now I'm just more puzzled. I don't understand why my eigen vector doesn't yield the desired diagonal matrix. I know that you can just assume the diagonalized matrix is just...
  5. David Koufos

    How do I know if my eigenvectors are right?

    For ##M = \begin{pmatrix} 2 & 2\\ 2 & -1 \end{pmatrix}## I found the characteristic equation: ##( λ - 3 )( λ + 2) \therefore λ = 3,-2##Going back we multiply $$\begin{pmatrix} 2 - \lambda & 2\\ 2 & -1 - \lambda \end{pmatrix}\begin{pmatrix} x\\ y \end{pmatrix}$$ Which gives \begin{matrix} 2x -...
  6. David Koufos

    Air resistance differential equation

    Would that make a big difference tho? I could always just set up the constant to be trivial.
  7. David Koufos

    Air resistance differential equation

    Thank you by the way Orodruin for mentioning that it's nonlinear. I'm doing some research on "homogeneous first-order nonlinear ordinary differential equations." I guess that's the kind of equation this is.
  8. David Koufos

    Air resistance differential equation

    I treated ## \int {\frac {\mathrm {d \dot{x}}} {\mathrm {\dot{x^2}}}}## the same as ##\int \frac {\mathrm{dx}} {x^2} = \int x^{-2} \mathrm{dx} = -x^{-1}##. So then I got ##- \dot x^{-1} = \frac {\mathrm {dt}}{dx} = \frac {1}{2m}\rho CA t##. Then multiplied and divided: ##\frac {\mathrm...
  9. David Koufos

    Air resistance differential equation

    Hello all, I want to say thank you in advance for any and all advice on my question. My classical mechanics textbook (Marion Thornton) has been taking me through motion for a particle with retarding forces. The example it keeps giving is: m dv/dt = -kmv which can be solved for: v = v0e-kt...
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