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1answer
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Conceptual Ice Water Equilibrium

We observe that when we apply pressure on on Ice Water equilibrium system then more of ice melts.. Ice(more Volume) + Heat ----><----- Water (Less volume) If we increase pressure then volume ...
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2answers
66 views

Why does the mass on the cart-pole have to fall?

Not sure if I am posting this question in the correct community, as it relates primarily to reinforcement learning. Apologies early on if this is not so. In reinforcement learning many algorithms ...
0
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1answer
29 views

Can there be net condensation into a pool of water?

I'm curious about the equilibrium of evaporation and condensation. Given that the surface area of a dehumidifier's evaporation coil at 4C is proportional to the rate of condensation, how would the ...
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1answer
46 views
0
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2answers
76 views

Equilibrium equations

You have one horizontal beam. Its left point is attached to a free pivot at the vertical wall. Its right point is suspended by a rope from the ceiling. Nothing is moved. So $\sum F=0$ and $\sum M=0$. ...
3
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0answers
121 views

Le Chatelier's principle and energy minimization

In Callen's "Thermodynamics" in section 8.5 he asks us to imagine some perturbation $dX$ of an extensive parameter of a system in contact with a reservoir that acts to hold fixed the intensive ...
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0answers
136 views

Thermal state vs equibilibrium state

Could someone explain what's the difference between a thermal state and an equilibrium state? Or is it even the same?
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1answer
69 views

Balancing a bowl of water

Let's say you have a mildly elliptical bowl balanced on top of a stick. This bowl is filled with water, not necessarily to the top but fairly full (I'm not 100% sure this makes a difference). You then ...
0
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1answer
175 views

How far does the man have to walk down the beam in order to tip the beam off fulcrum A? [closed]

I have set the sum of the forces in the y equal to zero and calculating the torque around B, I get that he walks 7.9. I don't have an answer key, but I don't believe this is the correct answer. I ...
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6answers
2k views

If the Earth is in constant motion then why do we say that an object is in a state of rest?

I got this question as my physics class homework for tomorrow. Anyone please help me out. If Earth constantly rotates and revolves, then how can we call an object in a state of rest?
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2answers
56 views

Pertaining to Newton's laws, how do so many objects acheive perfect equilibrium?

Suppose a light is hanging from a ceiling. Supposedly, the force of tension pulling it up is exactly the same as the force of gravity pulling it down. Why is it that the tension happens to be exactly ...
0
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1answer
136 views

Why is it effectively impossible to balance this rectangle block on a triangle block? (See photo)

I've always wondered why it's basically impossible to balance a rectangle block on top of a triangle one like this. This is my nine-year-old giving it a try. I have never in my life gotten it to ...
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3answers
343 views

Is it true that spring has more force acting on it at its positive maximum amplitude than than at the negative one?

Am I missing something? It seems obvious to me that at $+A$ and $-A$, the spring has restorative forces equal in magnitude but opposite in direction. But since gravity is always pulling it down, ...
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1answer
170 views

How exactly do walking canes and crutches help?

I am reading introductory physics, and there is a chapter on equilibrium. In the chapter, the author mentions how devices can exploit distribution of forces to help those that are physically ill, via ...
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1answer
52 views

How does phonon scattering change the distribution function?

For a one-dimensional structure, we know that the modified distribution function has the following energy dependency in equilibrium: \begin{equation} Z(\varepsilon)\,f(\varepsilon) = ...
0
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1answer
77 views

Boltzmann equation collisional operator in thermal equilibrium

Edited after Thomas' answer http://jila.colorado.edu/~ajsh/astr5770_14/grbook.pdf#section.30.5 Question 30.6. "Detailed balance": System is in thermal equilibrium, and the physics of the system is ...
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1answer
140 views

Exercise about equilibrium and virtual work [closed]

Two railway carriages of mass $M_1=2m$ and $M_2=m$ are on a 45° inclined plane. A spring, parallel to the plane, keeps both carriages in balance against the gravitational accceleration. The ...
3
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2answers
699 views

Why can't charge be in a stable equilibrium in electrostatic field?

I am reading Feynman's Lectures volume_II where he discussed the impossibility of the presence of stable equilibrium in an electrostatic field. There are no points of stable equilibrium in any ...
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1answer
38 views

Total Collapse in Understanding a Pulley

In the following system, the tension T is equal in magnitude to the weight W. But how can I set this up in a system of equations? This is my problem: $\Sigma F=0=\left( \begin{array}{c} 0\\ -W\\ ...
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1answer
221 views

Local and global detailed balance

I'm taking a course on nonequilibrium statistical mechanics and I encountered the terms local and global detailed balance. I'm a bit confused about what is their exact definition and what is the ...
3
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0answers
66 views

Is it possible to have a line rather than a point where the three states of a substance can exist?

Most of us are familiar with state diagrams that define which of the three states a substance will take given the pressure and temperature. And that some substances, such as water for example, exhibit ...
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1answer
219 views

Why should slope of pressure versus volume always be negative?

I read that the slope of the pressure, ($P$), versus volume ($V$) graph should always be negative for thermodynamic stability, but there was no further explanation in the text. Could someone give an ...
1
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1answer
687 views

Mechanical equilibrium : thermodynamics and classical mechanics

A similar question was asked here but mine is a bit different. In thermodynamics, a mechanical equilibrium is defined as a uniform pressure (for a fluid). In classical mechanics, equilibrium is ...
2
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2answers
188 views

Where do forces point in an equilibrium system

I have the system above, with three identical balls of weight $W$ and radius $r$. The angle joining the centres is $\theta$, and the coefficient of friction between the balls and the plane is $\mu$ ...
1
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1answer
552 views

How to calculate the normal force exerted by a fulcrum off-center?

So I know that $F_N$ exerted by a fulcrum right under the centre of mass for, say, a long horizontal rod, is equal to $mg$. But what if the fulcrum is off the centre of mass either to the right or the ...
0
votes
1answer
150 views

How many bricks can be put without disordering the equilibrium? [closed]

A homogenous brick with length L, is on a horizontal surface. On this brick are put one after another other bricks, which are the same with the first. Every brick is moved along L/5 units horizontally ...
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2answers
506 views

Checking for equilibrium in a square configuration of charges [closed]

Four equal positive charges each of magnitude q are placed at the respective vertices of a square of side length l. A point Q is placed at the centre of the square. Then find the state of equilibrium ...
0
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2answers
71 views

$N>2$ gravitating masses can never reach equilibrium [closed]

If you have $N>2$ point masses, each attracted to each other by the force of gravity, how could you go about showing that they will never reach equilibrium?
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1answer
287 views

Equilibrium when it shouldn't be?

I'm doing an experiment that requires me to balance a ring, tied to four strings, in the middle of a force table; in other words, the objective is to set the ring at equilibrium. Each string is ...
0
votes
1answer
200 views

Rotational Equilibrium Problem [closed]

The question is as follows: One end of a uniform 4.0-m rod, whose weight is w, is supported by a cable that makes an angle of 37° with the horizontal. The other end of the bar rests against a wall ...
0
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1answer
54 views

Temperature in a vacuum made in the lab

Is the thermal energy of a vacuum 0? And, how close to a perfect vacuum can we make in the lab?
0
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0answers
57 views

Deriving the Force on an ion in the Classical Harmonic Crystal

I was following Solid State Physics by Ashcroft and Memrmin and their introduction to the Classical Theory of the Harmonic Crystal. (Chapter 22) If there are a large number of ions in a straight ...
0
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1answer
46 views

Will heating water vapor induce equilibrium?

What happens to the vapor content if a mixture of gases saturated with water vapor is heated isobarically? Will the amount of liquid water present decrease, yielding up more vapor so as to ...
0
votes
1answer
173 views

Find the center of gravity of a system with three spheres [closed]

Three spheres are put on a table. The first sphere, whose mass is 1 kg is 20 cm away from the second whose mass is 2 kg and the third sphere is 100 cm away from the first sphere and has a mass of 5 ...
0
votes
2answers
223 views

What is the theoretical instantaneous temperature of a gas?

When we measure the temperature of a gas we typically integrate the molecular collisions and wind up with an 'average' temperature due to the sensor comprising a relatively large thermal mass. And ...
1
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1answer
138 views

Chemical reaction A+B$\leftrightarrow$C. Equilibrium VS Non Equilibrium

Could you please confirm or say why I am wrong? Let us consider the steady state of the chemical reaction $A+B \leftrightarrow^{k_+}_{k_-} C$, with $k_+$ and $k_-$ the forward and backward rates. ...
0
votes
1answer
299 views

Is equilibrum condition consequence of second law of thermodynamics?

Equilibrum state is generally stated to be most stable state. Is equilibrium state consequence of second law of thermodynamics at microscopic level. i.e a system tends to reach the equilibrium state ...
0
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5answers
682 views

Why am I not accelerated by the reaction force applied by Earth on me? [duplicate]

Newton's third law says that "to every action, there is always an equal but opposite reaction". And Newton's second law of motion says that, $F=ma$ $=>$ $a=\frac{F}{m}$. People says that If I stand ...
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1answer
178 views

What is thermodynamic equilibrium?

The state of thermodynamic equilibrium is typically defined referring to the system's behaviour in the future. Can the definition be formulated in terms of measurable quantities?
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0answers
48 views

Is the system in equilibrium?

If the time derivative of the Liapunov functional related to free energy of my system is zero, can I say my system is in chemical equilibrium?
2
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1answer
281 views

Extension of Lami's theorem

I was experimenting with the triple scalar product and forces in equilibrium when I came to this result: Consider 4 forces $ \pmb{F_i}$ for $i=1,2,3,4$. $\pmb{F_i}=F_i\hat{e_i}$ where $\hat{e_i}$ is ...
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2answers
205 views

Oscillations Near Equilibrium (With Linear Differential Equations)

Case I: The force acting on an object of mass m is $F(x) = F_o(1-e^{\alpha x})$ Case II: The force acting on an object of mass m is $F(x) = F_o(1-e^{-\alpha x})$ where $F_o$ and $\alpha$ are ...
1
vote
1answer
222 views

Balancing sphere

A cube is balanced on the very top of a sphere, and is given a small push in some direction, at which point it begins sliding down that side of the cube (due to gravity). Now, I want to keep the cube ...
3
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3answers
153 views

Average temperature of the universe

Is it possible to define some average temperature of the universe? If yes, what fixes this temperature and how t estimate today's temperature? Is it different from the temperature of the black-body ...
0
votes
1answer
57 views

simple physical system involving convergence to equilibrium at decreasing speed

I want to make an analogy of an economic model (Solow 1956) with a simple physical system that exists in reality. I am not looking for a mathematical formula to describe the system (I have that ...
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votes
2answers
598 views

Why are planets in unstable equilibrium in a stable orbit

It is well known that a planet in stable orbit is in unstable equilibrium. If e.g. the moon was just a few m/s slower in velocity, or a few m closer to the earth than it is, the gravity would ...
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4answers
2k views

Equilibrium using Center of Buoyancy and Gravity (Problem)

I don't understand a solution to a homework question. Specifically, I don't understand the logical sequence of each bolded statement in the answer. (b) To ensure that a ship is in stable ...
1
vote
1answer
305 views

Meaning of chemical equilibrium between two phases

Suppose two phases 1 and 2 of water, say ice and water, are kept in a closed container, at a fixed temperature $T$ and fixed pressure $P$? Then I have the following question: Is phase 1 in ...
2
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2answers
86 views

How's equilibrium possible here?

Here's the question.......Two point masses $m$ and $2m$ are attached at each end of a light rod. The rod is pivoted at the center and is free to move in a vertical plane. Then find the angle $A$ when ...
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1answer
140 views

Do the stars in a galaxy have a thermal kinetic energy distribution?

I think, there is practically everything given to that: many point-like masses, able to exchange energy pseudo-randomly, and far long enough time to reach a thermodynamical equilibrium. Of course, ...