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Apr
12
comment What's the problem with light traveling at speed higher than $c$?
@BenLindsay Sorry, trading precision for readability! Precisely: the same behavior that allows moving your head along a ripple of light, is the same behavior that made people predict that the Michelson-Morley experiment would find out how fast the Earth move through an aether. That behavior being "Galilean invariance", which is now known to not hold at high velocities.
Apr
12
answered What's the problem with light traveling at speed higher than $c$?
Apr
12
comment Would the moon be brighter if it were completely spherical?
@JánLalinský Ahhh you're right. I wasn't thinking about the dependence on Earth-Moon distance. Thanks for setting me straight :)
Apr
11
comment Zero Potential Energy Change in Raising a Mass
It has units of energy and is called "energy" ("kinetic energy" and "potential energy"). Walks like a duck and quacks like a duck...
Apr
9
comment Why did Einstein took speed of light unit or constant in his equation of relativity?
It's a bit rude to ask a question like this without first using google. What about the wikipedia page en.wikipedia.org/wiki/… is unsatisfactory?
Apr
8
comment Why do shiny surfaces reflect more light than other surfaces?
Could you make the title more descriptive? I'd answer the question, "Why do shiny surfaces reflect more light than other surfaces" with, "because that's how shiny is defined".
Apr
6
comment If we connect a block of p-type semiconductor only to a positive terminal, will it become positively charged?
This is false! I mean, for lab purposes sure, and no, the voltage difference on a battery doesn't completely specify everything, but the electric potential can be viewed as the result of a charge distribution, and so a change in potential means a change in the charge distribution, even if there's no obvious change to the naked eye.
Apr
6
comment Single slit diffraction - wave vs particle view
What's there to reconcile? $h/\lambda$ isn't the uncertainty in the wavelength...
Apr
5
comment Phase difference in SHM between spatial coordinate and velocity
You can't. One refers to a phase in the "angle" domain and one refers to a phase in the time domain.
Apr
1
comment Is it possible to travel near light speed and not notice relativity?
(Schwern's answer has more accurate numbers of course, I'm just ballparking!) The video effects are directly related to redshifting/blueshifting, whereas the coordinate system effects are consequences of Lorentz transformations and time dilation. My word of caution is that it's really the latter you want to focus on in understanding special relativity.
Apr
1
comment Is it possible to travel near light speed and not notice relativity?
Just as a comment: you really have to be careful as to what you mean by "see". Does "see" mean to write down an event in spacetime, in whatever physics equation you're working with? Or does "see" mean to actually have a little camera with a photosensitive surface inside it? The common statements would be, "the trip took five years in both Earth's and Proxima Centauri's coordinate systems", "a video camera on Earth looking at the spaceship's launch and landing would give a nine yr video", and "a video camera on Proxima Centauri of the launch and landing would give a 1yr video". [cont.]
Mar
29
comment Does this shadow diffraction effect have a name?
I see! Retracted my close vote.
Mar
29
comment What kind of unit is $m^2s^{-4}$ in terms of gyro/accel?
I think you need more to the question to make it meaningful. ie, someone could ask, "If $x=\frac{1}{2} g t^2$, what the heck is 'square time'?" but no one really cares! It's just an indication of how our quantities scale as our units scale. And certainly not every unit has to have a name!
Mar
29
comment Calculate divergence via partial derivative
Hint: $a\cdot r=a_x x+a_y y+a_z z$, $A=(A_x,A_y,A_z)$, so...
Mar
22
comment Why do tops move opposite to each other when colliding, not tangentially?
@NoviceC The fact that you have to bring up the issues of elastic vs inelastic, infinitesimal duration, shows to me that the argument isn't based on general conservation grounds and has to do with dynamics instead! At a moment in time there's no translational symmetry, and only a discrete rotational symmetry by 180 degrees, so I don't see what symmetry has to do with it either.
Mar
21
comment Why do tops move opposite to each other when colliding, not tangentially?
@NoviceC but it can't be a one-dimensional problem due to the angular momentum of the tops. The problem is two dimensional to begin with.
Mar
20
comment Why do tops move opposite to each other when colliding, not tangentially?
It really isn't. If the total linear momentum is zero, you can still have any arbitrary change in direction, so this doesn't explain why the collision has to be collinear.
Mar
19
answered Pendulum motion equation issue
Mar
19
revised What is the sign of the energy exerted by a man sitting in the back of a boat pulling a canoe?
added 78 characters in body
Mar
19
answered What is the sign of the energy exerted by a man sitting in the back of a boat pulling a canoe?