Questions tagged [volume]
The volume tag has no usage guidance.
477
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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 ...
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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? ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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:...
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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 ...
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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 ...
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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 ...
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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 ...
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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?
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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 ...
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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.] [...
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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 ...
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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 ...
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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 ...
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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 ...
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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?
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Dirac delta in Fourier space for finite volume
In some class notes about cosmology I have found the following claim. The author starts by stating that the Dirac delta is given by:
$$\delta^{(D)}(\vec{x}+\vec{x}')=\int\dfrac{d^3q}{(2\pi)^3}e^{i(\...
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Dependence on $(p,V,T)$ rather confusing
I am currently taking the freshman thermodynamics course and have asked several times for explanations of the relationships which can, and which cannot, and why they cannot. But I still don't really ...
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Does this theorem holds out for spacetime?
The theorem:
Let $F$ and $C$ be two finite geometric figures (those defined by two continuous functions in a given region $D$), where $F$ belongs to an $n$-dimensional Euclidean space and $C$ is the ...
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Haag’s theorem in finite volume
I’ve been reading on Haag’s theorem and found this proof that uses standard QFT instead of the axiomatic kind: https://arxiv.org/abs/2011.08875
It essentially boils down to saying that the vacuum ...
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Area of a $pV$ diagram [duplicate]
On a $pV$ graph (where the Pressure is on the Y axis, and the Volume is on the X axis), I am conceptually confused on how the area under the graph is equivalent to the work done by the system (...
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How does Pressure times Volume = Work Done?
I understand the equation mathematically-- $p$ times (change in) $V$ = Work done. However, I am confused about it conceptually. Work is (in a non-calculus context) constant force applied over a set ...
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Confusion on $pV$ diagrams
I am extremely confused on the concept of a $pV$ diagram.
I understand that Pressure times (change in) Volume equals the Work done by a piston; however, I am confused on how volume and pressure can ...
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What is the "volume of the gauge group"?
I often see the term "volume of the gauge group" and I am not clear on what this is referring to. For example, in the second volume of Weinberg (page 22), he says
...the volume of the gauge ...
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2 examples of molar volumes of binary mixtures
It‘s about the following task:
Figure: 2 examples of molar volumes of binary (2 components, i=A,B is the component index).
mixtures. Let V be the total volume of the mixture.
Using binary mixture as ...
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Boyle's law ( Volume and Pressure )
I am confused about the fact that (The volume is inversely proportional to the pressure)
I understand that when the atmospheric pressure increases the volume of our object decreases.
But why should it ...
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I have this simple yet confusing doubt about sign convention of work done on & by the system. Which factor to consider internal energy or vol.change?
Kindly explain whether we would have to consider energy added to system negative and vice versa within the case of work done on system?
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The actual proof of $\delta W = P dV$
All "proofs" of $\,\delta W = P dV\,$ that I saw involve some piston and a gas cylinder. But how to prove this is true in general, that whenever (or maybe under some necessary conditions) we ...
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Relative Fluctuations in volume at thermodynamic limit
Volume fluctuation of a pressure ensemble is given by
$$\langle(\Delta V)^2\rangle = k_BT\langle V\rangle\kappa_T$$
where $\kappa_T$ is the isothermal compressibility.
In the book, it is said that in ...
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What is the correct $pV$ diagram for gas expanding inside sealed cylinder covered with piston?
I am not sure about the correct $pV$ diagram for the isobaric process of gas expanding inside a sealed cylinder covered with a piston when it is heated with candle. The best I can come up is
The zig-...
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Thermodynamics - Unsteady flow energy equation
can anybody explain what happened to the PV term in (dE/dt) for the control volume (system). It is mentioned that changes in kinetic and potential energy is neglected and so dE/dt = du/dt, if change ...
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Proof of the valence $\lambda$ of a canonical transformation equaling its Jacobian determinant [closed]
Let $Q(q,p),P(q,p)$ be a canonical transformation with valence $\lambda$. The following is intended to be a proof of the following relation:
$$\lambda = \frac{\partial(Q,P)}{\partial(q,p)}.$$
Let $F(q,...
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Pressure over time in a tank with variable volume and an orifice
I have a tank whose one side can be moved, so we can change the pressure inside the tank by this movement. (In my main case this ig going to be a sinosoidal movement). We add an orifice to the tank, ...
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4
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Why do we use $P_{\rm ext}$ in the formula of $\int p \, dv $ work?
To what I can understand-in a piston cylinder arrangement, piston moves out due to net force experienced by piston due to difference between internal pressure of system and external pressure. So, the ...
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Specific volume formula for a fixed vessel not making sense
The specific volume $v_{avg}$ for the liquid-vapour mixture phase is given as $v_{avg}=m_fv_f+m_gv_g$
In the textbook, diagrammatically, this is shown as:
So, as the mixture is heated or cooled, $v_{...
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Why is specific volume calculated like this here?
In a solved example in Cengel's Thermodynamics text,
As they have stated, we don't know if the refrigerant is in compressed liquid form. In the case that it is, it's not necessary that the volume the ...
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On the finiteness of worldsheet area
It is commom to define the wordlsheet of a classical open string, for example, as the $2$-dimensional smooth manifold with boundary as $\mathbb{R} \times [0,\pi]$. With the appropriate embedding $X: \...
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How to interpret Liouville's equation?
In various texts, I see Liouville's theorem stated both verbally and as an equation. But it seems to me that these two formulations don't agree.
For example, in Wikipedia:
The distribution function ...
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Why do quantum objects slow down when volume increases?
I was reading this article about the EMC effect and saw this quote
“In quantum mechanics, anytime you increase the volume over which an object is confined, it slows down,” Schmidt says. “If you ...
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Why is there no law of physics that contains the Planck volume?
The Bekenstein-Hawking entropy of a black hole contains the Planck surface.
Mead's discussion of the gravitational microscope yields the Planck length as the length measurement limit.
Is there any ...
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Measure-preserving vs. non-dissipative vs. Hamiltonian systems
Are measure-preserving systems always non-dissipative? Phase space volume is preserved in both, according to Liouville's theorem. But are there any differences?
Are measure-preserving and non-...
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My textbook says one and the wikipedia and undergrad professor on quora other, which is correct?
I am learning about thermodynamics(1st law), and in my textbook it's stated that heat does not transfer from the isothermal process to the surrounding, but the undergrad professor(from quora, on some ...
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How can any of answers be correct? [closed]
Blue and orange curves are isotherms and I need to compare changes in Interal energies. In processes 1->2 and 2->3
I have options:
A) same value and same sign
B) almost same value
C) different ...
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Zwiebach String Theory, Quick Calculation 21.19 [closed]
In "A First Course in String Theory" 2nd ed. by Barton Zwiebach, on page 489 there is a problem to be solved. It seems like a simple plug and chug but I can't make it work out. Equation (21....
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Is there a fast way to get the net work from this figure?
I am trying to interpret this figure that shows the pressure-volume relationship in the lung of a human being. As I was taught in college, the area under a curve is the work done during a volume ...
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Volume of a sphere seemed when moving close to the speed of light
Let earth be a sphere of radius $R$. A person is moving with a relativistic velocity $v$ along one of the diameters of earth. What will be the volume measured by him?
Here as far as i know,the length ...
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