Questions tagged [density]
Density is defined as the mass per unit volume of a substance.
1,023 questions
2
votes
1
answer
233
views
Alternate statement for Liouville's theorem: Can you say that the relative velocity between any two representative points is zero?
So Liouville's theorem basically says the local density of representative points stays constant or that the flow of representative points resembles that of an incompressible fluid. Can you then say ...
- 31
0
votes
1
answer
83
views
How do I calculate the maximum possible atmospheric density/ surface pressure a planet can have?
I'm not entirely sure if this is the right stack but here goes.
I'm trying to design a fictional planet that has less gravity than Earth but I would like to give it an atmosphere as or even more dense ...
- 49
0
votes
1
answer
75
views
Non-Newtonian Fluid Density
When a projectile hits a non-Newtonian fluid, does the density of the fluid at the spot of impact increase?
- 39
1
vote
1
answer
224
views
Does low air pressure or low air density cause altitude sickness?
People usually say that "low air pressure (or more precisely, low partial pressure of oxygen) causes altitude sickness." But air pressure and air density both decrease roughly proportionally ...
- 52.3k
1
vote
1
answer
177
views
How precisely does the density of an object need to match the density of water to achieve neutral buoyancy?
The classic explanation I can find online is that something is neutrally buoyant when its density equals that of the fluid it sits in. For something like a boat, it can sink and increase its submerged ...
- 149
0
votes
1
answer
115
views
Why is the equation $P=ρgh$ valid even when there is a body submersed in the liquid? [duplicate]
The typical proof of $\Delta P=ρgh$ for a liquid is by taking a cylindrical element of it having height $dh$ and cross sectional area $dS$ at depth $h$. For the element to be in mechanical equilibrium,...
- 47
2
votes
1
answer
88
views
How is flowrate affected with pressure drop? [closed]
Assume $50\text{ gpm}$ at inlet of a pipe with pressure drop as $10\text{ psig}$. Will the flow at outlet still be same $(50 \text{ gpm})$?
Will a larger pressure drop will decrease the flow rate at ...
- 21
4
votes
1
answer
165
views
How to do physics on non-orientable surfaces?
Non-orientable surfaces don't have a volume form on it. How do you define the action principle without a volume form? I know somehow string theory is routinely done on non-orientable surfaces but I ...
- 463
1
vote
1
answer
217
views
How do we apply centrifugal force on everyday objects e.g. cream separator? [duplicate]
When I have a pebble attached to a string that I rotate, the reason that the pebble moves in a circle i.e. in constant distance from the center is because besides the centripetal force i.e. the ...
- 189
2
votes
2
answers
117
views
Let $\rho_0(x,y,z,t)$ be the initial mass density field then could we calculate its evolution with time using newtonian mechanics and how? [closed]
I've been trying to find a way to make this work but the only thing I have gotten to is that the integral of the mass density over space is equal to the total mass.
- 29
1
vote
2
answers
414
views
Is it possible to artificially create ice that is more dense than water? [duplicate]
I was reading this question that states ice is less dense than water because of the crystal structure being rigidly ordered and more far apart than in the liquid state. If this happens when ice ...
3
votes
2
answers
386
views
Is a black hole with zero energy density at its central singularity possible?
This paper https://arxiv.org/abs/2101.02012 analyses the Einstein field equations for a spherically symmetric shell of liquid matter, and seems to conclude that the gravity in the middle of such a ...
- 721
1
vote
1
answer
100
views
Is frequency of two strings, of same material that are joined together, same?
Consider a situation in which two strings of the same material (but different cross-sectional areas) are joined to form a large string stretched between rigid supports. Suppose there are 3 loops ...
- 51
-2
votes
1
answer
183
views
Increase metal density
If you were to compress a metal until its density is increase many time over would it keep this density or would it regain its normal density? And would such material be very hard or though?
1
vote
3
answers
380
views
Relation between temperature and density in adiabatic process?
I'm having trouble understanding the relationship between density and temperature during an adiabatic process. I know that in such a process, there’s no heat exchange, but I’m unclear on how exactly ...
0
votes
1
answer
201
views
Why are black holes referred to as infinite when their mass is not infinite and there is nothing infinite in the current universe? [closed]
Are they not actually just "really, really deep"? It seems like all the descriptions of them being infinite are actually people actually just saying they are "nearly infinite," or ...
1
vote
0
answers
95
views
Buyoancy with two liquids
A spherical ball of radius R is floating at the interface of two liquids with densities ρ and 2ρ. The volumes of the ball immersed in two liquids are equal.
Find the force exerted by the liquid with ...
- 11
-1
votes
1
answer
104
views
Should density be considered in the role of the strength of a gravitational field?
Ok, here me out. Black holes are usually formed from the compression of the mas released during the death of a supermassive star, however they have the same mass as the star (or even less). Yet when ...
1
vote
0
answers
100
views
How to construct the density matrix for the BCS wavefunction: $2 \times 2$ or $4 \times 4$?
Question Body:
In BCS theory, the ground state wavefunction for superconductivity is often written as:$
\Psi_{\text{BCS}} = \prod_{k} \left( u_k |00\rangle_k + v_k |11\rangle_k \right),
$
where$ |00\...
- 228
2
votes
1
answer
120
views
Evolution of Matter Density Under Newtonian Gravity
I want to examine the physics of gravity. This subject has two parts: how the gravitational field influences the behavior of matter, and how matter determines the gravitational field. I want to ...
1
vote
2
answers
165
views
If I drop a rock on the Sun, does it fall right to the center? [duplicate]
Hydrostatic equilibrium is what determines the diameter of the Sun. The internal gas pressure inside the sun equalizes with the pressure from Gravity on the outside. This is what determines the size ...
- 5,036
3
votes
1
answer
213
views
Radial distribution of ideal gas in a cylinder
today I have a computational doubt and a theoric one.
Starting with the theoric question, suppose I have a generic ideal gas in a cylinder and each particle is subject to a potential dependent on the ...
- 117
0
votes
4
answers
316
views
Are solids with the same density as air possible?
I was recently considering how to keep a super cheap ultrasonic range sensor safe from balls (or blocks, or whatever) going down ramps (or otherwise moving at high speeds) in a physics lab. It struck ...
1
vote
0
answers
80
views
How dense exactly is a vacuum in space (because of quantum fluctuations)?
You hear all the time that quantum fluctuations take up a given amount of energy in a vacuum, and this is how experiments such as The Casimir Effect gets the results that they do.
Have we actually ...
- 187
0
votes
1
answer
226
views
How to determine density of a granular material?
If you have a box full of granular material like sand grains and you know the diameter (possibly average) of the particles and the packing fraction (or volume fraction) with which they fill the space (...
- 1,487