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8h
comment Why can't the Navier Stokes equations be derived from first principle physics?
The Chapman-Enskog equation is the link between statistical mechanics and the Navier-Stokes equations that you allude to at the end.
11h
comment How to calculate Eulerian velocity from Lagrangian velocity
@CuriousOne Not sure why you are implying using Excel is a bad idea -- many experimental systems just dump the values they read into a CSV or Excel file and it's pretty common to manipulate data in those resulting files.
11h
comment Are there limits for the speed of sound? A maximum or a minimum only?
I'm really intrigued by the ideal gas result -- do you have a reference on why $\rho c^2/3$ is the upper limit for pressure? I haven't seen that before!
Jun
26
comment Leapfrog method in Particle-in-cell
Velocity (or position) Verlet methods are also useful here (also called Newmark methods in computational mechanics) -- these are related to the leapfrog method. Also, congrats on answering a question almost half-a-year after you left comments on it!
Jun
25
revised Frictionless and inviscid
deleted 14 characters in body
Jun
25
comment Frictionless and inviscid
@docscience I agree -- I think the author is trying to make the reader understand the difference between mathematical assumptions/approximations and physical properties.
Jun
25
answered Frictionless and inviscid
Jun
9
comment Does a rotating disk develop a potential difference between the centre and rim?
Isn't it possible to have a stationary wire where the two ends are in contact with the disk at all times? I assumed that's what he meant by "with suitable brushes" but maybe I misunderstood. But if there is no rotation of the wire, is there anything incorrect with @cag's answer?
Jun
8
comment Mean free path in spherical coordinate
And searching the internet for "steradian mean free path" or "solid angle mean free path" seems to bring up lots of lecture notes on the topic, so maybe that would help you until somebody comes along with an answer.
Jun
8
comment Mean free path in spherical coordinate
This is a topic that I recall was done pretty extensively when I took statistical mechanics, but I have neither my book nor my notes handy to look it up. I recall integrating over steradians a whole bunch though.
Jun
3
comment Why do dead batteries bounce?
How have I never heard of this before? Gotta go find some batteries...
May
27
comment If a liquid is compressed enough, would it become solid?
@igael It's possible. There is actually a planet theorized to have a surface of very hot ice, Gliese 436b. That awesomeness has been scaled back slightly, but it is still thought to have sub-surface hot ice due to the intense pressure/gravity.
May
27
comment If a liquid is compressed enough, would it become solid?
I disagree that increasing the pressure of liquid water at a fixed temperature will not create ice. Take a look at the phase diagram on this page. At 300 K, you can increase pressure to get Ices 6, 7, 10 and 11.
May
27
comment Does my mass really affect objects on the other side of the universe?
This addresses part of the question, but not what I would consider the most fundamental part -- if things like velocities, energies, etc. are discrete, is there an $r < \infty$ such that $F = 0$ due to, in essence, "truncation" of discrete values.
May
22
comment What speeds are “fast” enough for one to need the relativistic velocity addition formula?
@Ramashalanka much better, thanks for adapting to those of us who struggle :)
May
21
comment What speeds are “fast” enough for one to need the relativistic velocity addition formula?
I cannot tell which of those lines is red and which is not. I don't know if it's because I'm colorblind (seriously, I am) or if it's because of the format/being on my screen. I know which one is which because I know what the functions look like, but for others who may not, could you remake the plot with either much thicker lines so the different colors are obvious or with a dashed line to make it very clear which one is which?
May
18
comment What are the minimum necessary conditions for a static shock to ignite wood or grain dust in the air and cause an explosion or fire?
FWIW, I think this is perfectly on topic here. I think the chemistry.SE would be more interested in the chemical kinetics involved than in the physical processes that lead to something ordinarily safe exploding.
May
18
comment What are the minimum necessary conditions for a static shock to ignite wood or grain dust in the air and cause an explosion or fire?
One could imagine those fireballs in a confined environment and the destruction that would cause. And it's also possible that grain silos also have some fermentation going on which would result in a dangerous mix of combustible gases. The Boston Molasses Flood may be one of the crazier explosions due to fermentation in a silo.
May
18
comment What are the minimum necessary conditions for a static shock to ignite wood or grain dust in the air and cause an explosion or fire?
This is a great question. If you want to see what it looks like, almost any fine-particulate matter will combust. Coffee creamer for example, and sawdust.
May
8
comment Why do we (3 dimensional creatures) see in 2 spatial dimensions?
I'm voting to close this question as off-topic because this is about biology/perception and not physics.