Recent content by mr.hood

  1. M

    Coupled Pendulum/Mass on spring

    Homework Statement A mass M1 sits on a level frictionless surface attached to a spring of stiffness k. Mass M2 is supported from M1 by a string of length l. The horiztonal displacement from the equilibrium position of M1 is x1; the horizontal displacement of the pendulum from the wall where...
  2. M

    Java Using Scanner in Java to await user hitting return key

    Hi all, I've been trying to figure out how I can use the Scanner class in Java to pause my program and wait for the user to hit the return key. What I have now looks like this: Scanner kbd = new Scanner(System.in); kbd.next(); ... The thing is, the rest of my program won't run unless there...
  3. M

    Electric field inside a cavity within a uniformly charged sphere problem

    Homework Statement A uniformly charged sphere (center O1) with radius a and charge +Q has an off-center cavity within it (center O2) with radius b. Show that the electric field within the cavity is uniform and is directed along the line of centers, according to the equation: \vec{E} =...
  4. M

    Ziegler-Natta polymerization of ethylene

    Hi everyone, Does anyone know much about the Ziegler-Natta polymerization reaction? I used Spartan to find a transition state structure (specifically for the insertion of ethylene into Cp2ZrCH3+), and I'm supposed to use a molecular vibration (with an imaginary frequency, corresponding to...
  5. M

    Electric Field of a Long Charged Ribbon

    Scrap that last post, I treated this problem with sort of a surface integral and got an answer (an admittedly strange-looking one): First I used the equation: \vec{E} = \frac{1}{4\pi\epsilon_{o}} \int_{S}\frac{\sigma(\vec{r'})}{r^{2}}\hat{r}da' Part (a): \vec{E} =...
  6. M

    Electric Field of a Long Charged Ribbon

    Easy enough, thanks for the help! Edit: Haha not so easy I guess... I set up the following integral (for part (a)): \vec{E} = \frac{2\sigma}{4\pi\epsilon_{o}a}\int^{-a/2}_{a/2}\frac{dx}{x}\hat{x} When I integrate the 1/x from a/2 to -a/2, I of course get zero. Is my integrand...
  7. M

    Change Mobile Skin Back on MyPF - Help!

    Thanks, you're a life saver!
  8. M

    Change Mobile Skin Back on MyPF - Help!

    So I accidentally set my skin to "mobile," and now I can't figure out how to change it back because the "options" links no longer shows up in My PF. Help??
  9. M

    Electric Field of a Long Charged Ribbon

    Ok, so I guess I can treat the ribbon like a line of charge when I'm looking at it from a point on the x-axis... And is it safe to assume I should integrate across the width of the ribbon as well, because of the contributions of all the charge "behind" the edge I'm looking at? I would think I...
  10. M

    Electric Field of a Long Charged Ribbon

    Homework Statement A long uniformly charged ribbon is located in the x-z plane, parallel to the z axis, occupying the region -\infty \leq x \leq \infty and -a/2 \leq x \leq a/2. The charge per unit area on the ribbon is \sigma. a) Determine \vec{E} at (x,0,0) where x > a/2. b) Determine...
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