2,421 reputation
1520
bio website mathandcode.com/programs
location
age 21
visits member for 2 years, 7 months
seen 3 hours ago

16h
comment RC Circuit Analysis
In its current phrasing this sounds an awful lot like you want us to answer a multiple choice homework problem. Could you expand with what parts confuse you?
2d
comment How to simulate pendulum movement with high amplitude
khanacademy.org/computer-programming/forphys/6505289796943872 the "degrees" function turns radians into degrees, (multiplication by 180/Pi) which the trig functions need. no further explanation needed
2d
comment Parabolic slide
@Shadock also, since $\dot{x}(x_0)=0$ you'll run into an integral with a singularity at one bound of integration, but it has to be an integrable singularity. If it puts you off too much just take $\dot{x}(x_0)=\varepsilon\to 0$.
Apr
16
comment Period of a simple pendulum accounting for friction
Hi, there are surely lots of answers to this question on the website: physics.stackexchange.com/q/140943 physics.stackexchange.com/q/20478 etc. The keyword is "damped harmonic oscillator".
Apr
12
comment How did Planck derive his formula $E=hf$?
Just as a lead: what I heard was that Planck (or maybe someone else) discovered an exact form of the blackbody radiation formula which goes like $\nu^3 (e^{C \nu}-1)^{-1}$. He then spent months working backwards from this formula to try to find what physical assumptions he needed to get it, and he found quantization of energy levels in an oscillator $E=n \nu h$ did the trick. (C depends on $h$, $T$ and $k_b$). This is consistent with what is on en.wikipedia.org/wiki/Planck_postulate
Apr
12
comment How does the magnetic field generated from a rectangular cross-sectional current-carrying conductor differ from a circular cross-sectional conductor?
@AdamM-W Oh, you want to know how to numerically calculate it? That might belong to a separate question. High precision would probably be totally useless for you, for engineering/practical calculations, because only the highest order term $\mu_0 I/(2 \pi r)$ will be significant. At most, you'd go to a second order term (in a "multipole expansion"). Anyways, the formula in the paper you linked is just the integral of the vector potential of a wire (the infinitesimal wire can be taken as an infinitesimal "current element").
Apr
6
comment Would a spinning, evenly charged sphere generate a magnetic field?
@HolgerFiedler the magnetic field of a charged spinning spherical shell is exactly like a point dipole outside the surface: hep.princeton.edu/~mcdonald/examples/rotatingshell.pdf and is not "along the z axis", and Marcel's answer does not state that. The equations you are using are confused and are used without meaning. The equation $\nabla \times B=\mu_0 J$ contains different physics than the Lorentz force law.
Apr
6
comment Would a spinning, evenly charged sphere generate a magnetic field?
@HolgerFiedler it DOES mean rigid body, but all the FORCES involved are supplied by the structural integrity of the field. Your equation has nothing to do with the field actually generated by the charges. The Lorentz force law does not give you the field generated by the charges.
Apr
6
comment Would a spinning, evenly charged sphere generate a magnetic field?
@HolgerFiedler your formula would give the needed $\vec{B}$ field to support the charges moving in circles, as if the charged sphere itself had no structural integrity. Which is not relevant to the question that was asked. (That's why people are saying you're wrong -- "F" is irrelevant to the question asked so there's no reason why "$F\cdot qv$" should mean anything, let alone be zero).
Apr
4
comment Translation Operators
Well in one $\delta x$ is an infinitesimal scalar, and in the other $\hat{x}$ is an operator with finite eigenvalues. So the first expansion is incorrect.
Mar
30
comment Physics without time
"obviously"? I don't agree that a photon must have a rest frame, nor that if it did it would have the properties you describe...
Mar
29
comment Starter's book on Quantum Mechanics (more general and simple books than full QM textbooks)
@LandosAdam it's possible I haven't read his quantum mechanics book closely enough and that it's much worse than his mechanics book, I'll take another look over it tomorrow at a library.
Mar
29
comment Starter's book on Quantum Mechanics (more general and simple books than full QM textbooks)
@LandosAdam I haven't gone through his Quantum Mechanics book in much detail, but I know for sure his mechanics book is absolutely academic physics (from after the principle of least action). If you go to a bookstore, pick up the QM book, and can prove almost every major result in his book, then you're right: don't get it. Otherwise, you might be too critical.
Mar
23
comment Kepler's Laws to Determine Radius of Circular Orbit
Try plotting $r^{-2}-r^{-1}-0.01\cdot r^{-3}$ instead. The correction is small. $c^{-2}$ is small.
Mar
23
comment Similar effect to gravity horizontally?
Your calculations are wrong (you set force=energy, which is like saying "my clock reads five meters" - it doesn't make sense!) And your units are incorrect (your speed is a measure of acceleration). Are you expectong someone to fly towards the back of a moving truck when they jump? This is incorrect! If you jump on an airplane you notice nothing special different than jumping on the ground.
Mar
18
comment Insight into Torricelli's Equation ($v^2=u^2+2as$)
@pdmclean so that's the meaning of Torricelli's equation! It is an expression of conservation of energy and what it shares in common with Torricelli's law is that they were both formulated by the same person.
Mar
17
comment Water Waves in the Wake of a Boat
I don't think this is the case. Ex. i.stack.imgur.com/PaSas.jpg seems to have no asymmetry and the lines of constant phase (or maximums if you prefer) still bend outwards!
Mar
16
comment wave equation for a homegeneous prism object
In the 3 dimensional case, any serious book on optics shohuld include it. The key topic here is the Fresnel equations: en.wikipedia.org/wiki/Fresnel_equations keep in mind these equations are for solving the wave equation in three dimensions. The two dimensional case will be simpler.
Mar
15
comment Is there any theoretical limit to the distance at which particles can remain entangled?
1. there is no theoretical limit to the distance at which particles can remain entangled. 2. Quantum entanglement cannot be used for instant communication at a distance.
Mar
14
comment Why 'Force x displacement', and not momentum to measure energy?
relevant: en.wikipedia.org/wiki/Vis_viva#History