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Dec
6
revised Why are sine/cosine always used to describe oscillations?
deleted 6 characters in body
Dec
6
comment Why Electrostatic field has a continuous curve?
There is nothing very meaningful here. A field line is a curve $\vec{x}(t)$ for which $\vec{x}'(t)=\vec{E}(\vec{x}(t))$ for some vector field $\vec{E}$. In order to satisfy this equation, $\vec{x}'(t)$ must exist, so it can't have any breaks.
Dec
6
comment Elastic Collision of Infinitely Large Body and an Infinitely Small Body
You get indeterminates of the form $(\infty-\infty)/0$!!! Just solve the problem and take the limit $M\to\infty$, $m\to 0$ AFTER you find the solution.
Dec
6
comment Using the fourier series to analyze the motion of a finite string
The trick is to multiply by $\sin(k \pi x/L)$ and integrate from $x=0$ to $L$.
Nov
29
answered Geodesic equation (free particle)
Nov
29
comment Geodesic equation (free particle)
Can you add more details? You can't always choose a coordinate system where the geodesic equation is trivial everywhere.
Nov
29
comment Does voltage always cause current?
@user4205580 and that's because we don't care about the situation where a vanishingly small voltage gives you an infinite current, or where you can have a nonzero current with no EMF. If you're trying to consider such a case you're going to run into difficulties, because that's just not what Kirchoff's laws were meant for... but I am considering the case with a vanishingly small but nonzero resistance in the wire. In that case, my statement (both voltage drops are zero at the same moment in time implies current is zero) is true.
Nov
29
comment Does voltage always cause current?
@user4205580 and if the voltage drop across the inductor and the voltage drop across the source are both zero, in a real circuit you build, then the current is zero.
Nov
29
comment Does voltage always cause current?
@user4205580 There are lots of little nuances and this is the reason people usually talk about LR or LC or RC circuits. If you just have an "L" circuit, the current will be as high as possible until the "R" of the wire itself, the battery, or the inductor comes into play, and you have to treat things as a three component circuit. If you really did have zero voltage across $L$ and zero voltage across the battery (and you measure these things in a lab, so think of a real circuit here), there would be no current!
Nov
29
answered Does voltage always cause current?
Nov
29
revised How to prove the average velocity formula without calculus
added 308 characters in body
Nov
29
answered How to prove the average velocity formula without calculus
Nov
29
revised Can we find a vector if its dot product and cross product with another vector is given?
added 6 characters in body
Nov
29
answered Can we find a vector if its dot product and cross product with another vector is given?
Nov
28
comment How much work can the human body do before dying of exhaustion
Hi, this isn't the usual meaning of the word "potential energy" (because you're talking about useful work). I think it would help if you changed your title to "How much work can the human body do before dying of exhaustion", since that's the real question.
Nov
27
comment How can light follow curved spacetime?
The lesson of special relativity is that there IS no frame of reference where a photon is stationary. Not that such a frame "is a point".
Nov
24
revised Why does the critical angle for refraction exist?
added 746 characters in body
Nov
24
answered Why does the critical angle for refraction exist?
Nov
21
answered Clarification about first spherical harmonic
Nov
20
comment Special Relativity Kinematics Problem with My Wrong Solution
Is the question to find $d$? If so, could you edit that into your post?