Questions tagged [volume]

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What is the atomic composition of the human body, by volume?

According to Wikipedia, the composition (by atomic percent) of the human body is: 62% hydrogen 24% oxygen 12% carbon 1% nitrogen etc. Question: What is our volumetric composition*? *I get this is a ...
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18 views

Proving the rate of volume of flow of water through an inclined area

We have studied that volume of water flowing per second through a given area $a$ is v.a, where v is the velocity of water. I have tried to prove the same. I assume that a square area of side a metre ...
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1answer
27 views

Sanity check on meaning of Liouville's theorem

I've been studying Liouville's theorem lately. The statistical mechanics textbook by Kardar proves the theorem by showing that $dq\cdot dp$ is unchanged for each coordinate for an infinitessimal ...
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36 views

Is the total volume proportional to the number of identical sound sources?

What happens to the perception of loudness when 4 identical devices placed around the listener play a sound sample? Will they sound 4 times "louder" than 1 device? What if they're a bit out ...
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1answer
18 views

Measure volume/mass of a bag of water without weighing scale

I am trying to figure out the mass and/or volume of liquid inside a sealed plastic bag of about 150 litres (1x0.6x0.3m) without being able to use a weighing scale. Preferably, the measurement devices ...
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20 views

Is there any formula showing the relationship between $V$, $A$ and $G$ as mentioned below?

We all know that if we fill a cylinder with water and then drop the egg into the water it sinks but when we add some three tsp of salt the egg floats. Let, $V=$ volume of the cylinder. $A=$ Volume of ...
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1answer
295 views

Energy density of a 0D point particle vs. a 1D string

As I understand there is a problem in physics where point-like massive (or charged, etc.) particles would have infinite mass/energy (or charge, etc.) density. I'm curious how in the context of String ...
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2answers
46 views

If gases are not ideal at high pressures, why doesn't raising the temperature of a gas make it less ideal?

I'm learning about ideal and non-ideal gas behavior in Chemistry, and my textbook and online sources say two things : Gases behave ideally at high temperatures and low pressures. Gases behave non-...
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1answer
35 views

Derivative of internal energy with respect to pressure at a constant volume

I need to obtain the derivative of internal energy $U$ w.r.t. pressure $p$ at a constant volume $V$. Realizing that $\mathrm{d} U = T \mathrm{d} S - p \mathrm{d} V$, I rewrite $$ \left( \frac{\partial ...
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43 views

Density of States

For getting the density of states formula for photons, we simply multiply the density of states for atoms by 2 (due to two spins of photons). I am getting the 2D density of states formula as :- g(p)dp ...
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1answer
50 views

Calculating the compressed air by tides

I couldn't find any information on this topic. That is why I decided to ask in here. Can air be compressed by tides? I have an aquaponics setup next to the sea. When the high tide occurs, will you be ...
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1answer
578 views

Phase space volume doesn't change under canonical transform

I have given a set of generalized coordinates $(q_1,..q_n,p_1,..p_n)$. Suppose I had a canonical transform $(q_i,p_i)\rightarrow (Q_i,P_i).$ I am trying to show that the phase space volume element ...
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25 views

Phase transformation at constant volume $V$

A source heats water inside a vessel (V=constant). As soon as boiling begins, pressure raise up. How will the system evolve? Depends on the heat? How would be the relationship between the temperature ...
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1answer
621 views

Invariant Phase space volume under canonical transfromation

I have a volume element in phase space: $$ d\omega = \prod _{i=1}^{N}(dq_{i},dp_{i})$$ Now I should show the invariance of this product under canonical transformations. I think first I would have to ...
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280 views

Density function in phase space

What does density function in phase space physically mean? How does it indicate, the more familiar density that we are accustomed to ( an analogy may be), in phase space?
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1answer
35 views

What causes increment in volume when compressive forces are applied on an object

Doubt When compressive forces are applied on a body, what causes increment in volume. According to me the volume should remain constant since the mass and density of body are constant.
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2answers
37 views

2 gallon tank pressurized to 100 psi connected with a tube to a tractor tire with only 30 psi

2 gallon tank pressurized to 100 psi connected with a tube to a large tractor tire with only 30 psi. And the air does not move from tank to tire. Why? Can anyone link a YouTube video to explain ...
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1answer
33 views

How does the melting ice cube in a glass of water doesn't change the water volume? [duplicate]

that's problably a very noob question, and answer that i found is: the water volume was always the same, what is kinda obivius, but doesn't seen enought to me. So I can't stop thinking, were did the ...
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0answers
15 views

Force acting on a cube on all sides [closed]

A metallic cube of length L is stretched out uniformly by force F normal to each of its faces. Given Young's modulus and Poisson ratio, what is the deformation in the cube?
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45 views

Can you plot irreversible but quasi static processes on a $pV$ diagram?

I've often heard that you can't plot irreversible processes on a $pV$ diagram, but what about in the case where you have a quasi static process with friction? There still exists a curve of ...
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2answers
260 views

Quantification of entropy mathematically when $T$ and $V$ both change

$$ln\frac{W_f}{W_i}=N ln\frac{V_f}{V_i}=n N_a ln\frac{V_f}{V_i}$$ $$\Delta S=nRln\frac{V_f}{V_i}$$ $$ln\frac{V_f}{V_i}=\frac{1}{n N_a}ln\frac{W_f}{W_i}$$ $$\Delta S=\frac{R}{N_a}ln\frac{W_f}{W_i}=kln\...
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10 views

Does multiple outlets (at same level on tank) from an overhead tank increase pressure?

I have a tank that is about 1foot high from my shower, however the pressure(or volume) isn't sufficient. Is it possible to increase the pressure(or volume) at the showerhead by doing the following: ...
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2answers
205 views

Relation between surface area/shape and pressure

For a shape with a given volume and given gas pressure inside the volume, if the shape is changed to increase the surface area, will the internal gas pressure change?
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2answers
54 views

When differential of $p$-$V$ $dW$ work equals $-pdV$?

The differential form of the first law takes the form $$dU=\delta Q + \delta W$$ or $$dU=TdS-pdV.$$ First, we know that $TdS=\delta Q$ for reversible process. So we can't say that $dU=\delta Q -pdV$. ...
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3answers
51 views

What causes volume of sound to decrease with distance?

I know about the inverse square law however I do not know why it actually decreases. Does it have to do with sound absorption, it runs out of energy so the vibrations lessen or as distance increases ...
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1answer
222 views

Inmersion of homogeneous straight cone into a liquid

I have a problem with an exercise that I require help: Find the immersion of a homogeneous straight cone of height h and specific weight $\gamma_1$ in a liquid with specific weight $\gamma$. The ...
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2answers
15k views

Is it a coincidence that 1 liter water has a mass of 1 kg while 1 cubic meter has 1000 liters of water?

1 cubic meter has 1000 liters of liquid. Meter is a unit independent of kilogram. Then why does 1 liter of water at max density (4 °C) have a mass of 1 kg? Is it a mere coincidence?
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1answer
112 views

Lost volume data of water and isopropanol mixtures [closed]

WHO has two recipes for disinfecting, based on ethanol and isopropanol (IPA). They typically start with an alcohol volume and then top it off with the other ingredients to 10 litre. One of the recipes ...
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1answer
33 views

Why do some textbooks use $T$-$V$ diagram for temperature table instead of $p$-$V$ diagram?

I am confused about this thing. In the temperature table, the first column explains specific temperature and the second column explains corresponding saturation pressure. From what I understand, if ...
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1answer
51 views

In which dimension should nearest neighbor distances be calculated? Confusion regarding some concepts

In this paper, Abstract—The intrinsic dimensionality of a set of patterns is important in determining an appropriate number of features for representing the data and whether a reasonable two- or ...
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2answers
62 views

Why is tire pressure lower when parking and higher while driving (and not rise more when driving faster)?

I just noticed this whenever I park the car for a while, the tire pressure goes to a lower value on all tires, and whenever I start driving, it goes higher. The difference is not so big, but it is ...
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3answers
11k views

Calculate mass of air in a tyre from pressure

How can one calculate the mass of air inside a tyre, given a particular tyre size; a pressure, in $kPa = \frac{1000kg}{m\cdot s^2}$; and assuming room temperature, and normal air composition? I can't ...
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1answer
31 views

Crossings in the $p$-$V$-diagram of Thermodynamic cycles

Today I was tasked with correcting and grading a first year thermodynamics exam and one student drew a very peculiar diagram for the Ericsson-cycle. In the p-V-diagram the isothermal expansion and ...
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2answers
139 views

Time period of piston performing SHM

Suppose I have a closed piston-cylinder system which contains an ideal gas,and it is being compressed adiabatically by the piston which has a vertical orientation,and in doing so,the piston is ...
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1answer
39 views

How can a Diesel motor be drawn on a $pV$-diagram?

Only quasi-static processes can be drawn on a PV-diagram, because during a quasi-static process thermodyanamic variables such as pressure $p$ and volume $V$ are well-defined. However, for example, the ...
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23 views

What Are The Physics and Air Pressure Effects of Extremely Large Bells

How would one go about figuring out the physical properties of when a bell is hit. Can I parameterize the diameter of the bell, its height, and the kinetic force of the knock to get the volume in ...
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12 views

How does the distribution of entropy in the expanding universe evolve? [duplicate]

Also, Is the entropy divided by the volume of the (observable) universe increasing with respect to time or is that number decreasing, unstable, or constant, or infinite?
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1answer
102 views

Intuition of $dV$ in $PdV$?

I seem to have some misunderstanding of $PdV$ in the first law of thermodynamics. $$ P dV = T dS - d U $$ I have a ballon. I apply some work (or change the temperature inside the balloon). Now, ...
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3answers
144 views

Volume form in terms of the Levi-Civita Symbol

I'm currently reading Sean Carroll's book on General Relativity, and at some point he writes: First notice that the definition of the wedge product allows us to write \begin{equation} \mathrm{d}x^...
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1answer
56 views

Particle states per phase space volume of a quantum gas

Consider a quantum gas in a box with volume $V=L^3$ and temperature $T$, consisting of spinless bosons. Explain why the number $dN$ of "single-particle states" in a "momentum space volume" $d^3p$ is ...
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3answers
179 views

Boyle's Law and hot air balloon

A bit dumb question because it is really difficult to imagine it. :- Pressure is force per area. Talking about gases, the pressure is said to be the force molecules exert on walls of let's say a ...
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38 views

Demonstration of comoving volume between 2 redshifts

1) I can't manage to find/justify the relation (1) below, from the common relation (2) of a volume. 2) It seems the variable r is actually the comoving distance and not comoving coordinates (with ...
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2answers
483 views

Virial expansion in terms of pressure

I'm studying thermodynamics and I found two forms for the virial expansion: $$pV~=~RT[1+\frac{A_2}{V}+\frac{A_3}{V^2}+\ldots] \tag{1}$$ and $$pV~=~RT[1+B_2p+B_3p^2+\ldots]\tag{2}$$ my problem is that ...
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2answers
88 views

What does it mean for the Lorentz Transform to preserve areas?

If we look at the Lorentz Transform from some frame $S$ to some frame $S'$ moving relative to $S$... $$\begin{bmatrix} \gamma & -\gamma v\\ -\frac{\gamma v}{c^2}& \gamma \end{bmatrix}\begin{...
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3answers
10k views

Determine the Dependence of $S$ (Entropy) on $V$ and $T$

Why can the equation $$dS= \frac{1}{T} dU + \frac{P}{T} dV$$ be expressed as $$dS= \left. \frac{\partial S}{\partial T} \right|_V dT + \left. \frac{\partial S}{\partial V} \right|_T dV \quad?$$
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22 views

Change in entropy due to the change in volume

If its given that $N$ no of Ideal gas atoms are in $V$ volume. What will be the change in entropy in units of $N\cdot kb\cdot\ln2$ when the volume is increased fourfold, i.e. $V \to 4V$, keeping ...
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32 views

What is the volume inside the inner event horizon of a Kerr black hole?

(Dokuchaev 2011) found periodic orbits of particles and photons inside a Kerr-Newman black hole with a maximally extended global geometry. They orbit inside the inner horizon $r<r_-$ where the $r$ ...
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2answers
43 views

Pressure and volume [closed]

Currently, I am working on this experiment where I hit a balloon with a small object so that the pressure inside a balloon changes. The pressure increased when I hit the balloon, but I need to ...
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2answers
2k views

How constant volume gas thermomether keeps the volume constant?

So the level of mercury on the left is being kept down by the pressure of the gas, correct? When the temperature rises, shouldn't the mercury level on the left go down? And when the mercury level go ...
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3answers
97 views

Dilemma of volume displaced by an object

I have 2 questions, the second question is based on the answer of the first question 1.)When an object floats, is the volume of the object submerged and displaced water equal? 2.)So if volume ...

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