Questions tagged [equilibrium]
Equilibrium is the condition of a system in which all competing influences are balanced. These can range from forces (static/dynamic equilibrium), to chemical processes (chemical equilibrium) and temperature gradients (thermal equilibrium).
884
questions
0
votes
0
answers
32
views
Help solving this mechanics problem [closed]
Between a push cart and a pull cart, which requires the greater "effort"? For consistency, both weighs 500 N, has a handle bar inclined 30° above the horizontal and a coefficient of sliding ...
0
votes
0
answers
23
views
What is the minimum value of $\mu_s$ that will allow rod $AB$ to remain in place? The rod has length 3.3m and it has weight of 200N [closed]
First, I have properly drawn the Free Body Diagram (attached below) and mentioned all forces.
Since the system is in equilibrium, the sum of all vertical and horizontal forces will be zero. This ...
- 31
4
votes
0
answers
65
views
Empirical equivalence of shifted chemical potential $\mu_i$
It is often said that, in classical thermodynamics, entropy $S$ and energy $U$ are defined only up to an additive constant proportional to the total amount of substance $N=\sum_i N_i$ (where the sum ...
- 41
0
votes
0
answers
21
views
Vapour mass to remove from tank in VLE to reduce a certain amount of pressure [closed]
I have a tanktrailer and a tank containing a cryogenic VL-mixture of methane. I would like to calculate how much kg of Boil-Off gas I would need to take out from the tank to the trailer in order to ...
- 11
1
vote
2
answers
65
views
Weight distribution and support polygon
I was working on a problem of supporting an object with sticks and wondering about some use cases that would fail.
My approach is to place the n-sticks (for example 4) under an object with mass m ...
- 11
0
votes
2
answers
52
views
What happens to entropy and energy when you inject heat into 2 systems in thermal equilibrium?
Below we have a system A and B in thermal equilibrium. What happens to the entropy and energy of the systems when you inject heat into system A and let it equilibriate further? I know that heat will ...
- 1
1
vote
3
answers
99
views
Is the pressure zero in thermal equilibrium? [duplicate]
In a canonical ensemble, we have $dU=TdS-pdV$. When we are in equilibrium, the energy $U$ is minimized. This implies that $\left(\frac{dU}{dV}\right)_S=0$. Since $\left(\frac{dU}{dV}\right)_S=-p$, we ...
- 1,288
0
votes
0
answers
26
views
Thermal equilibrium, heat and temperature [duplicate]
I am just studying thermodynamics for the first time and confused between these three terms
Temperature is defined in terms of thermal equilibrium (from zeroth law of thermodynamics) and thermal ...
- 355
1
vote
1
answer
49
views
Total temperature when combining two systems of unequal temperature [closed]
I know that intensive properties a characterised by the fact that when you combine two systems (A and B) that have the same value of an intensive property (for example same Temperature) the combined ...
- 121
1
vote
2
answers
91
views
What is the total energy of newtonian polytrope stars of index $n > 5$?
In classical newtonian theory, we could find a general expression for the gravitational potential energy of a polytrope sphere (of pressure $p(\rho) = \kappa \rho^{\gamma}$, where $\gamma = 1 + \frac{...
- 7,023
0
votes
1
answer
28
views
Lower bound of stable equilibrium for mass on rotating ring
Consider a point mass $m$ constrained to move without friction along a ring of radius $R$. The ring rotates with angular frequency $\omega$ about the $z$-axis which runs through a diameter of the ring,...
- 1,257
0
votes
1
answer
67
views
System in thermal equilibrium with reservoir
Let's say I was trying to build Statistical Mechanics from scratch. I had studied the microcanonical ensemble and made the following definitions:
$$\frac{\partial S}{\partial E} = \frac{1}{T},$$
$$\...
- 2,143
3
votes
1
answer
76
views
How fast do $\rm CO_2$ molecules transfer between air and water at equilibrium?
Suppose a bath of water is in equilibrium with the air above it at temperature T and pressure P. The concentration of $\rm CO_2$ in the air is, say, 400ppm, and the concentration of $\rm CO_2$ in the ...
- 475
0
votes
0
answers
30
views
How does this tensegrity structure work?
How does this structure work? Where is the centre of gravity in this case?
1
vote
1
answer
74
views
What is the equation of state (EoS) of a polytrope in general relativity?
I'm trying to numerically integrate the TOV (Tolman-Openheimer-Volkof) equations, using Mathematica. The code works, but I'm having issues with the polytropic equation of state (EoS). The equations ...
- 7,023
1
vote
0
answers
37
views
Intravenous therapy - why does blood come out of my body once the fluid is depleted? [closed]
The other day I wasn't feeling so well so I visited a doctor. He recommended that I take a break and get intravenous therapy so I did. I laid on a bed and the nurse inserted a needle into my left arm ...
- 11
1
vote
2
answers
105
views
Coordinates of center of gravity in non-uniform gravitational field
The following is a textbook problem where one is asked to find the $x$ and $y$ coordinates of the center of mass AND those of the center of gravity in a non-uniform gravitational field:
The location ...
- 123
0
votes
3
answers
87
views
Why does a reverse reaction occurs everytime?
In a chemical reaction, I have studied that a reverse and forward reaction occurs every time and neither reactant nor product can be zero.
My question is: if the forward reaction and the backward ...
- 177
1
vote
1
answer
45
views
Calculate new equilibrium of cryogenic LNG tank after addition of new cold LNG
Disclaimer: I am not a physicist, but I am trying to unravel this problem and it is interesting me more and more the more I work and think about it.
I have the following problem:
There is a Cryogenic ...
- 11
2
votes
1
answer
288
views
Numerically solving the TOV equations: how to find the max radius and mass?
I'm solving the TOV (Tolman-Oppenheimer-Volkoff) equations using Mathematica 13.2, and I'm having some issues at finding the outer radius $r_{\text{max}}$ and mass $M_{\text{max}}$ of the spherical ...
- 7,023
2
votes
1
answer
155
views
Same temperature implies thermal equilibrium
A particularly weak formulation of thermodynamics is
Two bodies are said to be in thermal equilibrium if no heat transfer occurs when they are put in diathermal contact. Thermal equilibrium is an ...
- 2,277
0
votes
1
answer
29
views
How does a particle in a medium return to its original position in case of sound propagation?
I know that particles don't go from one end to the other, they just vibrate and transfer sound energy to next particle. How do they return to equilibrium again? Do they return just after collision ...
0
votes
5
answers
137
views
What is equilibrium position in a pendulum? Will there be only one equilibrium position in the motion of a pendulum?
Equilibrium position of a pendulum is defined as the position where no external force acts on the body and if no force is applied, it remains at rest. In the image, isn't gravity acting everywhere, ...
0
votes
0
answers
47
views
2 rods connected at a pivot and attached to a spring
I have a question concerning this problem
First I calculate F1 by taking the origin at F2 and imposing equilibrium for the torque thus getting $ F_1 = \frac{a}{a+b} F $ and similarly for F2, then I ...
1
vote
1
answer
76
views
Confusion about thermodynamic equilibrium
I’m studying thermodynamics and statistical mechanics from the book by Kerson Huang. I’m having a conceptual difficulty with the notion of thermodynamic equilibrium.
At the beginning of the first ...
- 321
1
vote
2
answers
104
views
Conditions for the Virial theorem
I've been investigating the Virial Theorem, and I've found different conditions, some more restrictive than others, for it to be applicable to a given system. According to my professor, said theorem ...
- 197
1
vote
2
answers
34
views
Does physical equilibrium occur at specific temperature and pressure?
Does physical equilibrium occur at only specific temperature and pressure? Like does equilibrium occur only at $ 1 atm $ and $0⁰C$ between water and ice? If I change temperature or pressure will the ...
- 13
1
vote
1
answer
62
views
Different definitions of equilibrium in statistical mechanics
Statistical mechanics tries to predict macroscopic behavior of a thermodynamic system from microscopic considerations. Suppose we are dealing with system with phase space $\Gamma = (\Lambda \times \...
- 959
0
votes
1
answer
35
views
A system can be in motion in thermodynamic equilibrium? [duplicate]
I mean thermodynamic equilibrium implies mechanical equilibrium, but mechanical equilibrium doesn't mean to that the system to be in static equilibrium. For some reason, all the systems I have seen in ...
- 41
1
vote
3
answers
70
views
What is exactly thermodynamic equilibrium? [closed]
As I wrote in the question, what is thermodynamic equilibrium? From what I understand is a state where the thermal, chemical properties don't change with respect of the time and there is a mechanical ...
- 41
1
vote
1
answer
80
views
Doubt: Arnold's "Mathematical Methods of Classical Mechanics", pg. 18
I am having trouble understanding the following diagram from pg. 18 of Arnold's book:
I am unable to see why local maxima of the potential energy correspond to unstable equilibria (and, reciprocally, ...
- 165
0
votes
1
answer
56
views
Identifying minimums in gravitational wells in General Relativity
According to the Newtonian gravitational potential:
$$\phi\left(r\right)=-\dfrac{GM}{r}.\tag{1}$$
We can find the minimum possible point in a gravitational well as the one for which the value of the ...
- 503
1
vote
1
answer
45
views
Doubt on thermodynamics equilibrium
Is thermodynamics equilibrium related to mechanical equilibrium in anyway?
For eg if the net Torque on a system is not zero does that still mean the system can be in thermodynamic equilibrium?
2
votes
1
answer
50
views
Osmotic pressure "equilibrium"?
Consider a box with two compartments separated by a semipermeable membrane. The first compartment is initially at pressure $P_0$ and contains the solvent ; the second compartment is initially at ...
- 135
0
votes
2
answers
110
views
Difference between Displacement from Equilibrum and Amplitude of SHM
I'm currently studying Simple Harmonic Motion. What is the difference between the amplitude of the simple harmonic motion, and its displacement from equilibrium?
- 3
0
votes
1
answer
30
views
Equilibrium position for double spring hanging vertically [closed]
I feel a bit daft asking this but how do you calculate the equilibrium position of a system with a spring (spring constant k1) hanging from the ceiling with a mass (m1) attached to the bottom, and ...
0
votes
0
answers
35
views
Equilibrium position of $ n $ free charges as polynomials roots
The classic problem of the electrostatic equilibrium positions of a linear system of $ n $ free unit charges between two fixed charges is well known, here an example with $n = 1$.
Few days ago I found ...
- 101
9
votes
4
answers
1k
views
What maximizes entropy? [duplicate]
Liouville theorem states that the phase space distribution function of a system remains unchanged with the system evolution,
$$
\frac{\text{d}\rho}{\text{d}t}=\frac{\partial \rho}{\partial t}+\sum_{i=...
- 56.8k
3
votes
0
answers
25
views
Terminology of different equilibria?
I've heard many equilibrium terms:
Translational equilibrium
Rotational equilibrium
Static equilibrium
Dynamic equilibrium
The different terminology is slightly confusing. My understanding is as ...
2
votes
1
answer
45
views
Free body diagram of two cards leaning against each other [closed]
here is my body diagram:
he have the two weights two normals and two frictions however I think I am missing something becaused I only have cosine components when analysing the torque eq with respect ...
- 111
0
votes
1
answer
57
views
Deriving chemical equilibrium constant from non-reacting or reacting ideal gas mixture partition function?
Given a chemical reaction of ideal gasses:
A <-> B
From my understanding, there are two partition functions that you can write depending on whether A and B can react to form each other.
Non-...
- 179
0
votes
1
answer
119
views
Why the harmonic series appears when we stack a pile of books?
lets say we have some books resting on the floor.I am trying to find the maximum protuberance that the books can achieve.we see that the books on top of the initial book must have the center of mass ...
- 111
3
votes
1
answer
399
views
How can two black holes merge without violating No Hair? [duplicate]
Before two black holes merge, their individual event horizons must be perfectly spherical due to the No Hair theorem. If they weren't they'd be betraying information about the inside. After merging, ...
- 59
5
votes
2
answers
160
views
Do chemical potentials stay constant in chemical equilibrium?
I am uncertain whether chemical potentials stay constant during chemical equilibrium.
Consider a closed container divided into two parts 1 and 2 filled with ideal gas particles. The barrier between ...
- 218
0
votes
1
answer
38
views
Equilibrium of rods and stress
Reading through Theory of Elasticity, Landau & Lifshitz, I got stuck in the The equations of equilibrium of rods, on page 82. The part I do not understand is the following:
"We denote by $\...
- 115
0
votes
0
answers
21
views
Comparison of time to thermal equilibrium
I suddenly got curious in real life.
The refrigerator stops working when it reaches a set temperature.
If a hot object enters the refrigerator, the temperature of the refrigerator will rise and it ...
- 117
1
vote
1
answer
54
views
How much force is each leg supporting? [closed]
Assuming that the plank rotate in the red dot and it weights 10kg, how can we calculate the weight or force each leg is supporting?
I tried the following system, assuming the left most leg is ...
- 11
2
votes
1
answer
132
views
An axiomatic approach to thermodynamics
I have been working on an axiomatic approach to thermodynamics, and tried to follow the footsteps of Theodoro Frankel using his little book, The Geometry of Physics.
The passage appears before ...
- 630
1
vote
6
answers
144
views
How can an irreversible isothermal process exist?
An isothermal process is one in which temperature of the gas is constant throughout the process.
From my physics textbook:
the state of a gas is described by specifying its pressure $p$, volume $V$ ...
- 128
2
votes
3
answers
311
views
Visualizing the center of mass of a stickman toy
I have this metallic stickman toy that is able to balance itself. I am curious about its center of mass. Can anyone help me visualize a rough position to where the object's center of mass is with an ...
