John Rennie
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99/100 score
 Nov 26 comment Why escape velocity doesnot depend on angle of projection Hi Joey. The question I've linked explains why the escape speed doesn't depend on direction. It's because energy is a scalar not a vector. Nov 26 reviewed Approve Why escape velocity doesnot depend on angle of projection Nov 26 comment Why is the trajectory of the alpha particle in a cloud chamber almost straight? My recollection of beta ray trails (in a cloud chamber) is that they are visibly lss well defined than alpha ray trais precisely because they are scattered more. Very high energy particles, e.g. electrons from collisions in the LHC, do travel straight. If you want to know why very high energy particles travel in straight lines then that would be worth a new question. I'm tempted to over-simplify and say it's because very high energy particles have a high relativistic mass, though my fellow physicists would condemn me for even mentioning relativistic mass :-) Nov 26 revised Is there a relationship between kinetic energy of emitted electron and photoelectric current? Typo Nov 26 answered Is there a relationship between kinetic energy of emitted electron and photoelectric current? Nov 26 comment Why are harmonic oscillators quantized? A macroscopic mass on a macroscopic spring won't have quantised energy levels, even in principle, because it won't remain coherent for long enough. Quantum oscillators are quantised and describing them is a routine part of any quantum physics course. If you're interested you need to go off and read up about it. Describing the details here would require a review length answer. Nov 26 answered Galileo 5 and 6 satellites testing gravitational time dilation Nov 26 comment Why don't we include angular acceleration while calculating net acceleration for a particle moving in a circle ? @IshitaGupta: The difference from Newton's 2nd law is that mass is a scalar so $\vec{F}$ and $\vec{a}$ point in the same direction. Nov 26 comment Quantum Mechanics in your face Yes, Coleman does say that. Coleman is essentially describing the many worlds interpretation of QM. Incidentally this is an excellent lecture and I strongly recommend it to amateur physicists - experienced physicists will find it rather basic though quite fun. Nov 26 reviewed Close What is the potential difference between $a$ and $b$ in this basic circuit, when the switch is open? Nov 26 reviewed Close How do quantum particles interact with each other? Nov 26 comment How do quantum particles interact with each other? I'm afraid it's unclear what you are asking here Nov 26 comment Quantum Mechanics in your face I'm voting to close this question as off-topic because it's about what Sidney Coleman said not about physics Nov 26 revised What is the general relativity explanation for why objects at the center of the Earth are weightless? Clarify Nov 25 answered Working of electric-tester Nov 25 reviewed No Action Needed Stokes' theorem in complex coordinates (CFT) Nov 25 answered Why does the mass on the cart-pole have to fall? Nov 25 revised Why is the trajectory of the alpha particle in a cloud chamber almost straight? Oops Nov 25 comment Why is the trajectory of the alpha particle in a cloud chamber almost straight? @MartyGreen: true but a few multiples of very small is still very small. Nov 25 answered Head on collision of two black holes