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comment Particle Outside the Box
The wave function will have a discontinuous derivative if the potential contains a Dirac delta function. You can see this by integrating the Schrödinger equation (see en.wikipedia.org/wiki/…).
Sep
19
answered When is momentum not conserved?
Sep
19
revised Which is the lightest thing in this universe? Is that a photon or neutrino?
changed formatting of hbar
Sep
19
suggested suggested edit on Which is the lightest thing in this universe? Is that a photon or neutrino?
Sep
16
answered Dirac Notation Question Appearing In a Projection
Sep
11
revised Add air resistance to projectile motion
added 1631 characters in body
Sep
10
comment Add air resistance to projectile motion
I'll try to update my answer some time today with a python script to solve the equations of motion.
Sep
10
revised Add air resistance to projectile motion
added 16 characters in body
Sep
10
answered Add air resistance to projectile motion
Jun
20
awarded  Yearling
Jan
24
awarded  Enthusiast
Jan
14
answered Why doesn't Newton's Second Law include higher-order mass?
Jan
14
comment Commutator of $L^2$ and $X^2$, $P^2$
I just went through the derivation of that identity, starting from (1) $U^{\dagger}\left(R\right) {\hat V}_i U\left(R\right) = R_{ij} {\hat V}_j$ with $U\left(R\right) = 1 - i \delta\theta \hat{\bf n} \cdot {\hat{\bf L}} / \hbar $ and $R_{i j} = \delta_{ij} + \delta\theta n_k \epsilon_{k j i}$. So I just need to think a bit more about where (1) comes from, and why this means $\hat{V}$ is a vector operator. I guess from the usual definition of a vector as something that transforms like a vector under rotations.
Jan
13
comment Commutator of $L^2$ and $X^2$, $P^2$
I don't want to derail this question, but I've never quite understood the last part of your answer about how an identity like $\left[X_i, L_j\right] = i \hbar \epsilon_{i j k} X_k$ means $X_k$ is a vector operator. Any good references or intuitive explanations for that?
Jan
13
revised Lorentz force equation from relativistic Lagrangian
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Jan
13
answered Lorentz force equation from relativistic Lagrangian
Jan
6
revised Aerodynamic drag on a cannonball?
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Jan
6
answered Aerodynamic drag on a cannonball?
Jan
6
answered Energy of electron accelerated by a magnet
Jan
5
revised Bound States clarification
added 640 characters in body