Recent content by Bobbo Snap

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    The Force of an Array of Perm. Magnets on a Large Iron Body

    To 1ledzepplin1: I originally wanted to use electromagnets as well. My advisor, who worked in aerospace for many years, believes that generating enough power to operate the electromagnet for any significant period of time will be the problem. I'm using the permanent magnet array at his...
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    The Force of an Array of Perm. Magnets on a Large Iron Body

    They wouldn't. I suppose slow-pull would be a better name in this case but slow-push is what it's called in the literature. "Slow-push methods" encompass a multitude of techniques that are designed to work over an extended period of time, as opposed to a nuclear blast, kinetic impact, etc.
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    The Force of an Array of Perm. Magnets on a Large Iron Body

    For my senior physics research project I've developed an orbital analysis program that calculates the minimum \Delta V required (applied in an instantaneous impulse) to deflect an inbound Earth impacting asteroid. I've generated data for several different hypothetical orbits and now my advisor...
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    Line Image of a Charged Cylinder

    Thanks, that does look like the geometry of this problem. I think the ratio \rho_1/\rho_2 is the constant M it's asking for but I'm not sure how the potential values were found. I will study it some.
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    Line Image of a Charged Cylinder

    Anyone? Am I correct in thinking that the image is on the other side of the plane? Any hints on how to to find M ?
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    Line Image of a Charged Cylinder

    Homework Statement A long conducting cylinder bearing a charge \lambda per unit length is oriented parallel to a grounded conducting plane of infinite extent. The axis of the cylinder is at distance x_0 from the plane, and the radius of the cylinder is a . Find the location of the line...
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    Two suspended charged particles, find the angle from vertical.

    I don't think I can assume small angles, nothing is mentioned about the length of the string. But I do feel like there is some simplifying assumption I'm missing.
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    Two suspended charged particles, find the angle from vertical.

    Homework Statement Two particles, each of mass m and having charge q, are suspended by strings of length l from a common point. Find the angle θ which each string makes with the vertical. Homework Equations F_e = k \frac{q^2}{r^2}, \quad F_G = -mg, \quad F_T = \text{tension on string}...
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    First order perturbation question

    \langle \psi_3^0|H'|\psi_1^0 \rangle = \frac{2 \alpha}{a}\int \sin{\frac{3 \pi x}{a}} \sin{\frac{\pi x}{a}} \delta(x - a/2) = \frac{2 \alpha}{a} \sin{\frac{3 \pi}{2}} \sin{\frac{\pi }{2}} = - \frac{2 \alpha}{a} I worked out something like this for all three terms (m=3, m=5, m=7). Is that the...
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    First order perturbation question

    Homework Statement Suppose we put a delta function bump in the center of the infinite square well: H' = \alpha \delta(x -a/2), where \alpha is constant. a) Find the first order correction to the allowed energies. b) Find the first three non-zero terms in the expansion of the correction...
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    The rotational analog of Ehrenfest's Theorem

    Thanks PhysicsGente, your expression is exactly what I keep getting. That is, [H, r \times p] = [H, r]\times p. Maybe my mistake is trying to follow a solution I found which includes an extra term. It begins with the commutator reversed though, like this: [r \times p, H] = r \times [p, H] +...
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    The rotational analog of Ehrenfest's Theorem

    Homework Statement Show \frac{d}{dt}\langle\bf{L}\rangle = \langle \bf{N} \rangle where \bf{N} = \bf{r}\times(-\nabla V) 2. Homework Equations . \frac{d}{dt}\langle A \rangle = \frac{i}{\hbar} \langle [H, A] \rangle The Attempt at a Solution I get to this point...
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    Another Question About Angular Momentum in QM

    Ok, so I can simplify that last equation to get [L_z, H] = \frac{1}{2m}[L_z, p^2] + [L_z, V] =\frac{i\hbar}{2m}(p_y^2 -p_x^2) + [L_z, V] How does this imply V must be a function of r? (I guess I should have seen this from the form of the Hamiltonian).
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    Another Question About Angular Momentum in QM

    Homework Statement Show that the Hamiltonian H = (p^2/2m)+V commutes with all three components of L, provided that V depends only on r.Homework Equations In previous parts of the problem, I've worked out the following relations: [L_z,x] = i\hbar y, \quad [L_z,y] = -i\hbar x, \quad [L_z, z] =...
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    Griffiths Quantum Mechanics: Solving Angular Momentum with Commutators

    Oh, never mind. I think I can commute momentum and position operators acting on different variables. So xp_z = p_zx .
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