Recent content by castusalbuscor

  1. C

    Rate of evaporation of a spherical drop

    Homework Statement The rate of evaporation of a spherical drop of liquid is proportional to its surface area. Derive R(t) assuming constant density, where R(t) is the radius of the drop as a function of time. Homework Equations I know that the surface area of the sphere is A = 4 \pi...
  2. C

    Proving Trig Derivatives: Bessel Functions Explained

    This was actually brought up in class the the professor shot it down, he also shot down expanding it in a Taylor series (since we need to know the derivative for it to work). The limit definition might be more appropriate. ^_^ Thanks! I wonder is there a geometric way to prove it?
  3. C

    Proving Trig Derivatives: Bessel Functions Explained

    So its pretty much common knowledge that: \frac{d}{dx}\sin (x) = \cos (x) But how does one go about to actually prove it? This came up in my Math Methods class while we were talking about Bessel Functions.
  4. C

    Complex Analysis - Contour Intergral

    Homework Statement The problem is to integrate: \oint_{C}\frac{dz}{z^{2}-1} C is a C.C.W circle |z| = 2. Homework Equations The Attempt at a Solution I used the Cauchy integral formula: \oint_{C}\frac{f(z)}{(z-z_{0})^{n+1}}dz = \frac{2 \pi i}{n!}f^{n}(z_{0}) Which...
  5. C

    C/C++ Solving C++ Complex Array with Time-Dependent Schrodinger Equation

    Yeah, I just tried it and it did not work. using cout << complex<double>(1,5) does indeed output (1,5). However, when I use complex<double> a; a = complex<double>(1,5); cout << a; I get (5,0). And when I use std::cout << (1, 5) << std::endl I still get (5,0)
  6. C

    C/C++ Solving C++ Complex Array with Time-Dependent Schrodinger Equation

    Hi, I've been trying to write a program to solve a propagation of a wave packet using the time dependent schrodinger equation. and I noticed I would need to use complex numbers. I know that I need to use #include<complex> I declare my array, and I started with a simple 1-d array...
  7. C

    The Fourier Series of Sin^5(x)

    Solved? I ended up going with \frac{1}{\pi}\left( \frac{sin((n-5)x}{32(n-5)} - \frac{sin((n+5)x}{32(n+5)} - \frac{5sin((n-3)x}{32(n-3)} + \frac{5sin((n-1)x}{16(n-1)} - \frac{5sin((n+1)x}{16(n+1)} \right)^{\pi}_{-\pi} and I just plugged in \pi and -\pi. I talked to one of the "smart"...
  8. C

    The Fourier Series of Sin^5(x)

    Homework Statement So I have to find the Fourier series for sin^{5}(x). Homework Equations I know the a_{n} in: \frac{a_{0}}{2} + \sum^{\infty}_{n=1}a_{n}cos_{n}x + \sum^{\infty}_{n=1}b_{n}sin_{n}x goes to zero, which leaves me with taking the b_{n}. The Attempt at a Solution So what I got...
  9. C

    Finding Roots of Neumann Function N_n(x)

    Sounds doable.. will. report back with success or failure.
  10. C

    Finding Roots of Neumann Function N_n(x)

    I've never used Mathematica, though there seems to be a lot of people mentioning it. The prof wants us to use either C/C++ or FORTRAN. I have some experience with C++ so that's what I would be using. Also I would be compiling it in Unix/Linux, if that helps... Found an equation on Wikipedia...
  11. C

    Finding Roots of Neumann Function N_n(x)

    So for an assignment I have to write a program to find the roots of the Neumann function N_{n}(x). However the only Neumann function I have in my class notes is: Which is not overly helpful, and its the only one that was "boxed" in class. Any hints on how I can incorporate that into a...
  12. C

    Time-dependant Schrödinger Equation Help.

    I have a project to work on that's due by mid March. I would need to write a computer program, to show how a wave packet reflect off a barrier? How much of the wave reflects off a wall of finite height and thickness, and how much tunnels through? I remember doing something similar in my...
  13. C

    How Do You Calculate the Force to Separate Two Hemispheres?

    So today I was bouncing some ideas off one of the smart kids in my class, and was asking for some direction. The way he suggested I approach it was through density. The big arse integral I had to integrate which give the required answer was: F = \int\frac{4GM^{2}r^{3}sin\phi cos\phi d\phi...
  14. C

    How Do You Calculate the Force to Separate Two Hemispheres?

    Yes. the solution is \frac{3M^{2}G}{4a^{2}}
  15. C

    How Do You Calculate the Force to Separate Two Hemispheres?

    [SOLVED] Forece Between Two Hemispheres I am trying to study for my classical mechanics final, and the prof hinted that this problem would be on the final. Two uniform rigid hemispheres eachof mass M and radius a are placed in contact with each other so as to form a complete sphere. Find the...
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