dmckee

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bio	website	inspirehep.net/…
	location	Duchy of Grand Fenwick
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Experimental particle physicist. These days I'm doing neutrinos.

	21,520 reputation	bio	website	inspirehep.net/…	visits	member for	2 years, 6 months
22671 badges		location	Duchy of Grand Fenwick		seen	11 hours ago

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1d	comment	Short-duration forces Note, I've removed many incorrect (in standard English usage) spaces before punctuation marks. I left the ones in the quote because I have not seen the source, but unless you cut-n-pasted that from an authoritative source those are almost certainly wrong as well.
1d	comment	Short-duration forces This "In circular motion , it is said that the centripetal force acts only for a very very short period of time" appears to be a misunderstanding. The analysis presented considers a short interval of time so that only a small error is made be neglecting second order effects, then calculus is applied to get the solution in the limit of vanishing time steps making that approximation rigorous. All applications of calculus to physics work this way.
1d	comment	Where does the extra equation come from to determine the forces from an object on a table? I never studied this class of problems in detail, so I am hesitant to offer a prescription. If you are taking a engineering statics class you'll see some finite-strain treatments later in the class.
1d	comment	Hexadecapole potential using point particles? Ah, I see. The arrangement into point, line, square cube is not necessary. The arrangement of three charges -q at (-d,0) ,+2q at (0,0) and -q at (d,0) is also a pure quadrupole, and there are others. Look for a formal definition of what makes a n-pole.
1d	comment	Hexadecapole potential using point particles? Surely you've noticed a pattern in the four cases you quote. Maybe you can deduce the next step in the sequence. (Might be best to not worry about the word you would use, and just concentrated on the arrangement.)
2d	comment	Terminal velocity of all falling objects is same? Ah, a chance to get all sciency. Drop a feather and a tennis ball side by side and draw your own conclusion.
2d	comment	Can a linear momentum generate angular momentum at collision? It is also worth noting that if you look only at one part of a system you can give it some new angular momentum $L$ by doing some work (but you are ignoring the $-L$ that you have imparted to the other part of the system).
2d	comment	Can a linear momentum generate angular momentum at collision? You can look at this on several levels. At the lowest level there was a pre-existing angular momentum between the hand and the ball and some is transferred. At the next level out you had to push on the ground to move the hand and that does modify the Earth's angular momentum at some level. But not necessarily "sapped" it depends what direction the pushes are in. The guarantee it that $L_{\mathrm{Earth},i} + L_{\mathrm{you},i}+ L_{\mathrm{ball},i} = L_{\mathrm{Earth},f} + L_{\mathrm{you},f}+ L_{\mathrm{ball},f}$ (all measurements around some inertial center).
2d	comment	Electric dipole moment, which charge is the $q$ for? You book no doubt sets this up with a particular situation. Look back at how they defined it...
2d	comment	How long would it typically take to develope nuclear weapons these days? Related (but also closed) question where you will find some relevant comments: physics.stackexchange.com/questions/38626/… and physics.stackexchange.com/questions/31047/….
2d	comment	Collision between a photon and an electron "I could claim that the diffraction pattern observed in the double-slit experiment is due to compton scattering, among other factors." The cross-section for Compton scattering can be measured and is a simple function of angle that does not correspond to diffraction patterns. I know that pop-sci books make it seem reasonable to think about physics in terms of word pictures, but you must learn the math.
2d	comment	Increasing Amps I'm treating this as a practical questions---from a physics point of view the answer is that you simply need a higher current supply or to ration your power consumption, but you already figured that out.
May 22	comment	Collision between a photon and an electron I can't speak to the downvote, but adding a link to a n-page pdf and expecting you reader to page through it is not making things easy for someone you are asking to help you. The question appears to concern itself with the backwards limit of Compton scattering.
May 22	comment	Can one define a “particle” as space-localized object in quantum field theory? This derivation is effectively done in the momentum basis---which is just a valid and correct as the position basis---but because these excitations have well defined momentum Heisenberg tells us that viewed in that basis they do not have well defined position. To get the thing that you are used to you need to pick a basis in which both position and momentum are roughly localized; that's the wave-packed formalism that Trimok talks about, but it is mathematically difficult and we mostly calculate in momentum space.
May 22	comment	Calculate the distance between two points from iPhone Camera Without a stereoscopic view you must either know the distance to the target or find a calibration from pixes/second to linear-distance/second. I am, however, wondering if light field cameras can drag the range out of the data. Wouldn't that be spiffy?
May 22	comment	How can the big bang occur mathematically? See physics.stackexchange.com/q/7838 and physics.stackexchange.com/q/2355.
May 22	comment	The Sine pattern of variation This simply reflects what kinds of problems you've studied to date.
May 22	comment	The Sine pattern of variation Concerning the close reason. I might also have chosen "Not constructive" in reference to the lets list stuff flavor I see, but either way it needs work.
May 22	comment	The Sine pattern of variation Welcome to Physics.SE, nerdy. The short answer is "Yes, sinusoids show up a lot.", but we don't do make-a-list questions here and I am not able to understand this in any other way. Feel free to edit if you want---it can be re-opened--but please take some time to read out FAQ.
May 22	comment	Electric and Magnetic Field This may be the core of a fine--if very basic--question on the Lorentz force law, but right now it is very unclear.