# Questions tagged [volume]

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### Upthrust and displaced volume [closed]

Consider a boat which had a fixed weight. In Fresh water (smaller density), the upthrust provided is smaller than in salt water (larger density). So while both boats float, the one in fresh water is ...
73 views

### Confusion about the "Volume" in Archimedes principle

In Archimedes principle $F_b = \rho gV$. $\rho$ = density of fluid, $V$ = volume displaced by the fluid, and $g$ = gravity. If you have an object in the air, like a balloon, how does the volume work? ...
132 views

### Number of fog droplets in the air

I have an issue with the official solution to this problem from BelPhO: Visibility on the road is 100 m. Assuming that the diameter of a fog droplet is 1 micron, estimate the concentration of fog ...
55 views

### How is volume defined and measured in nuclear physics, in particular regarding the Sun’s core? [closed]

The Sun’s core is, from the micro/quantum perspective (from what I've read) the constantly moving phenomena of nuclear fusion (as the Earth is mostly the constantly moving phenomena of stable atoms ...
61 views

### Enthalpy of a Van der Waals gas continuation

In my previous question Enthalpy of a Van der Waals gas, I got the expression of the enthalpy generalised, but I am still having issues finishing it since it might have some quite hard calculus... For ...
43 views

### Doubt with the heat capacities

We know we can write the internal energy as: $$dU=\frac{\partial U}{\partial T}dT+\frac{\partial U}{\partial V}dV=C_v dT+\frac{\partial U}{\partial V}dV$$ and things started to not make sense, is it ...
119 views

### Do neutron stars (or really dense stars) contain more volume inside of them than the expected $V=\frac{4}{3}\pi r^3$?

If I understand correctly neutron stars are so dense that general relativistic effects are not negligible anymore. Does this mean that the volume inside of neutron stars is bigger than we would expect ...
32 views

### Volume element of the neighborhood of a surface

In this paper by da Costa, he derives the geometric potential arising due to the confinement of a quantum particle to a surface. However, I believe this physical context is not relevant to my question:...
1 vote
52 views

### Why do the litre and cubic metre volumes of cylinder natural gas not correspond?

A $47L$ cylinder says it contains $8.4m^3$ of natural gas at $137$ bar pressure. Could someone explain how we get from $47L$ to $8.4m^3$ ? I’m not an expert and thought they should be different by a ...
1 vote
128 views

### Evolution of volumes in Phase-Space

Liouville's theorem states that the volume occupied by an ensemble does not change as the ensemble evolves. My question regards the volume of the smallest sphere that contains the ensemble. Is there a ...
63 views

### Why are temperature and specific volume independent properties in thermodynamics?

If we have a sealed piston-cylinder with gas inside and we heat it from the outside, the temperature changes. At the same time, if we look at it as a control mass system,the volume increases as the ...
23 views

### How does loudness decrease with distance? [duplicate]

Let's say there's a speaker in a huge open space on the Earth's surface. The speaker blares a sine wave with frequency $f$ Hz and and volume $V_0$ decibels. How does the volume (in decibels) decrease ...
140 views

### Why do we usually measure liquids and gases by volume?

Why do measure liquids and gases in volume rather than by weight? Isn't that comparatively more inaccurate since volume changes with temperature and pressure?
63 views

### Gauge symmetry and the volume in phase space

Recently, I am reading a paper about the soft theorem and large gauge symmetry which is non-zero in the boundary. In section 6, the author introduces the covariant phase space method to illuminate why ...
106 views

### Why expansion work, $pdV$, is considered to be zero in nozzle?

Why $pdV$ work considered to be zero for flow of gas, say ideal gas, at low mach number through a converging adiabatic nozzle? [though total enthalpy remains constant, static enthalpy does change.] [...
31 views

### Triple Integral of Volume Concentration

I am working on a problem involving volume concentrations which are defined as: $$\phi_i=\frac{V_i}{V}$$ and are thus dimensionless. My problem is in $3$D and I have assumed that the components in ...
65 views

### Invariance of a volume element in phase space: What does it means?

I have been reading the third edition of Classical Mechanics by Goldstein, in particular, chapter 9 Poisson Brackets and Other canonical invariants. And it is shown that the magnitude of a volume ...
1 vote
81 views

### Why $p= -\frac{\partial U}{\partial V}$?

In Callen's book, in page35 he defined $$p= -\frac{\partial U}{\partial V}$$ where does it come from? I thought it might come from a reversible process where $dU=dQ+dW=TdS-PdV$（If the amount of ...
1 vote
44 views

### Calculate Change in Tank PSI per breath at depth

I am a scuba diver, trying to understand some physics that occurs throughout a dive. Primarily I am trying to understand the surface air consumption (SAC) derivation. For those unfamiliar, SAC is the ...
101 views

### Why chemists usually only deal with enthalpy and not internal energy? [duplicate]

From what I understand, enthalpy only seems like a mathematical intermediate step. Why do we have a special name for it?
1 vote
107 views

1 vote