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2d
awarded  Notable Question
Mar
8
awarded  Custodian
Mar
8
reviewed Reject (Why) is dumping liquid nitrogen on your head dangerous?
Feb
21
awarded  Critic
Feb
21
comment Why are electromagnetic waves called waves even though they don't travel through a medium?
-1 Saying "waves are called waves because they are solutions to a wave equation" completely inverts the rationale. The equation is called the wave equation because it describes waves. Waves came first, and the equations describing them came second and were named after them, not the other way around.
Feb
16
answered Why does it take a projectile as long to get to its apex as it does to hit the ground?
Feb
4
comment Is there a limitation on Gauss' law?
Single point field falls as $1/r^2$. Infinite line falls as $1/r$. Infinite plane is constant. What do you expect infinite volume to do? $1\times r$?
Jan
15
comment What will be the equation of motion of driven pendulum for amplitudes beyond the small angle approximation?
@Danu: Okay let me know when you've deleted your first comment and I'll delete my comments too.
Jan
15
comment What will be the equation of motion of driven pendulum for amplitudes beyond the small angle approximation?
@Danu: I'm not sure what you mean. The Taylor series is obtained by differentiating the original function and matching its derivatives with those of a polynomial... it's not like the infinite series comes out of the blue and then you define the linearization as the first 2 terms of the infinite series. You derive the linearization without ever having to think the higher-order terms, it's not like you have to first compute them and then suddenly drop them.
Jan
15
comment What will be the equation of motion of driven pendulum for amplitudes beyond the small angle approximation?
@Danu: Did you notice & click on the link in my comment? The linear approximation doesn't depend on the Taylor series, rather than Taylor series combines the linear approximation with higher-order approximation... I feel like it's backwards to put it the other way.
Jan
15
comment How hard would I hit the ground on Mars?
@Vogel612: The thing with stopping durations is that they can very a LOT. A stone floor has a much shorter stopping duration than a rug, and both are reasonable. Your glass will probably break when dropped on a hard floor but not a soft one.
Jan
14
comment How hard would I hit the ground on Mars?
@RubberDuck: Impulse is Newton-seconds, it basically means "apply a force F for T seconds". It should make sense that the force applied depends on the time over which it is applied, so the answer can't be in Newtons unless you specify the stopping time duration.
Jan
14
comment How hard would I hit the ground on Mars?
By force do you mean impulse?
Jan
14
comment What will be the equation of motion of driven pendulum for amplitudes beyond the small angle approximation?
@Danu: Is it?
Jan
12
accepted Is the world Markovian according to modern theories (QM, GR, etc.)?
Jan
12
comment Is the world Markovian according to modern theories (QM, GR, etc.)?
+1 your point about derivatives makes me wonder how many higher-order derivatives do you need to have maximum information? For example, in a classical sense, I would guess position and velocity together should be enough and that acceleration is unnecessary, but I don't know if this is true... any thoughts on this?
Jan
11
asked Is the world Markovian according to modern theories (QM, GR, etc.)?
Jan
11
comment Curvature of spacetime as a real thing?
@barongbaron: What do you mean it must be "into" another dimension? Imagine compressing a piece of foam into various shapes... it doesn't suddenly become 4-dimensional does it?
Jan
9
comment Why is surface charge distribution uniform for a conducting sphere? Can't it be arbitrary?
It's kind of subtle but I want to point this out: the symmetry argument is more or less a lie; it doesn't really work when we're talking about particles. (Imagine if only two electrons existed on a sphere... would the solution still be spherically symmetric?)
Dec
20
comment Why isn't length contraction permanent even though time dilation is?
"Permanent" means "true for all later times"... not sure what the space equivalent would be.