# 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).

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### Find tension in string [closed]

Find tension in the strings My try: If a rod is tied with 3 light strings in different different so to find tension in all the string we need 3 equation 1 we get from dynamic equilibrium 2 we get from ...
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### Torque equilibrium problem

We have a stick which is connected to the wall with a rope, like shown in the picture. I need to set the resulting torque to $0$, since it's in equilibrium. The solution in the textbook says: Pick a ...
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### Statics and torque equilibrium problem [closed]

This is a ladder, which is connected to a wall with a string (at the bottom - F is the tension in the string). It is in equilibrium at 60 degrees. I understand that I have to set the result of the ...
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### For what kind of thermodynamic systems are phase diagrams valid?

I understand that thermodynamic systems can be broadly categorized as open, closed or isolated. Do 2-D pressure vs. temperature type of phase diagrams apply to all three? Additionally, for closed and ...
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### Can two particles ever be in equilibrium under their mutual gravitational forces alone?

Can two particles be in equilibrium under the influence of their mutual gravitational forces alone? Obviously, if the two particles are kept at rest at a distance apart, one will exert an attractive ...
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### A paradox while explaining the equilibrium of books

An even number of books (say four) are held in the manner shown in the figure. It is obvious that if we apply a large force inwards, we can increase the normal force, and hence the friction which ...
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### Equilibrium in physics

We know that harmonic oscillator or pendulum will not reach a equilibrium at infinite time. But why a system of gas molecules reaches equilibrium (entropy of an isolated system will tend to increase ...
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### Two interacting blackbodies (one inside another) - when will thermal equilibrium be attained? [closed]

As I understand it, an ideal blackbody absorbs (and subsequently starts emitting) all incoming radiation. In typical setups like determining a planet's temperature given its albedo and distance from a ...
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### Statics problem from classical mechanics

I was solving David Morin's book on classical mechanics. In the solution for the second part of the "a" part of the question, why is the normal force defined as $Ndθ$ and not just $N$? Is ...
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### Intuition for imaginary time Greens function

I understand that $$G^M(0,0^+) = \operatorname{tr}\{\rho O_2 O_1\}$$ (I am not putting hats on the operators here because they don't render in the correct position) is simply the expectation value of ...
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### Thermodynamic work and potential functions

I was reading about the maximum thermodynamic work of a system (Z) that is going to equilibrium. $$dZ = dU + p_0 + T_0dS$$ I then came across the thermodynamic potential ...
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### Why must solids in equilibrium become crystalline?

In Landau's Statistical Physics's analysis of solids, he begins with the remark that solids are caracterized by their atoms' small oscillations about equilibrium positions. However, he states that ...
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### How does this tensegrity table work?

I have assembled below a desk toy which seems to defy laws of physics at first glance (objects can be placed on top of it up to a certain limit, since it is already under strain). The toy is in fact ...
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### An object is connected to the end of a spring and is immersed in water. What are the forces acting on the object? [closed]

The actual question is A copper piece of mass 10g is suspended by a vertical spring. The spring elongates 1 cm over it's natural length to keep the piece in equilibrium. A beaker containing water is ...
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### What is the difference between a reversible process and an equilibrium? [closed]

I am confused about the differences between a reversible process and an equilibrium when considering their energy aspect. Here is what I know so far. (1) Equilibrium and Reversibility Equilibrium ...
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### Serway & Jewett's definition of rotational equilibrium

On p. 364 of Physics for Scientists and Engineers (9th ed.), Serway and Jewett define a rigid object to be in rotational equilibrium if it has an angular acceleration of zero. They then state that a ...
1 vote
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### How do differently colored objects reach the same temperature if they are completely isolated together?

Imagine a perfectly reflective container, filled with vacuum and two bodies with different colors, i.e. they have different emissive and absorptive properties. The bodies don't touch each other or the ...
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### Pressure difference between a box and the outside atmosphere

Say I have a box of volume $V$, with an ideal gas inside it with temperature $T_b$. I don't know the number of particles inside it. The box is surrounded by the room's environment, which has ...
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### Investigating the stability of a wooden block

Consider the above experimental design. At the end of the strip, at point $p$, a mass $m$ is attached, the stability of the wooden block above is determined by the angle $θ$ at which the block topples ...
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### Water level in pipe higher than surrounding body of water

I had a question about water pressures and level. We've recently drilled a near vertical hole underground 130m deep by 400mm in Dia into flooded lower underground workings as part of a de-watering ...
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### What regulates the size of our atmosphere?

Our atmosphere is only about 100km thick before the official start of space. That is a mere 1.57307% of the radius of Earth (6,357km). The difference between the gratitational force at sea level and ...
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### Does a single ball undergoing ideal simple harmonic motion count as being in thermodynamic equilibrium?

(Posting this and deleting a previous similar post to make the question more clear.) Suppose we have an isolated system inside a box consisting of a spring and a ball attached to the spring. The ball ...
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### Why does Equilibrium shifts towards more dense phase while increasing pressure for phase change Equilibrium?

I recently read that when pressure of system in phase change equilibrium is increased, it shifts towards denser phase. So, in case of Melting of ice, increase in pressure results in shift towards ...
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### Doubt regarding proof of Earnshaw's Theorem using Gauss's theorem

While proving Earnshaw's theorem using Gauss's theorem, we consider a small sphere surrounding our test charge, and apply Gauss law on this sphere, stating that field from all external charges must ...
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### Why charges reside only on the surface on conductor?

I wonder why charges reside only on the surface on conductor? And I read this question and the answer to it: Why charges reside on the surface on conductor? https://physics.stackexchange.com/a/210634/...
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### Charge separation equilibrium equation for non-rotating blackhole at Eddington limit with spherically symmetric accretion?

What is the formula for equilibrium charge on a non-rotating black hole with spherically symmetric hydrogen-1 inflow at the Eddington limit of luminosity based on photon scattering acceleration of ...
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### Classification of equilibrium configurations for particles subject to elastic force constrained on a circle

I am interested in classifying all the possible equilibrium configurations for an arrangement of $l$ equal point particles $P_1, P_2, . . . , P_l$ $(l > 2)$ on a circle of radius $R$ and centre $O$....
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### Lami's Theorem Problem

Lami's Theorem states that the magnitude of each force in an equilibrium state consisting of three coplanar, concurrent forces acting at a point is directly proportional to the sine of the angle ...
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### Equilibrium constellations of classical point charges in hollow conductors

As far as I know, in free space there can be constellations of $N$ point charges in electrostatic equilibrium (albeit unstable equilibrium) for all $N$ except $N=2$. Some discussions here already ...
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### The forces acting on the tensegrity structure

Are these the only forces acting on the body. I assumed the COM to be somewhere there in between. since the tension in main string doesnt perfectly coincide with COM theres a small torque being ...
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### How do particle acquire thermal distribution?

Consider some toy N-body simulation: we start with a bunch of particles, discretize time, and simulate their interactions at each timestep. What numerical features should the simulation include to ...
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### On beam suspended by wires

My question involves sample problem 9-8 of the book "Physics" by Halliday, Resnick and Krane, 5th edition. So I could understand the answer given but there is something that is not ...
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### Gravitational Null Points in a system of point masses

For an equilateral triangle formed by 3 point masses which has a circumradius 'a' there are 4 null points: The centroid and 3 other points on the angular bisectors of the three sides. On calculation ...
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### Is a body in uniform circular motion in equilibrium?

I know this question has been asked a myriad different times, but nowhere can I seem to find a definitive, final resolution to it. Is a body in uniform circular motion in equilibrium?
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### Regarding the relation between statistical equilibrium and thermal equilibrium

I've seen a similar set of questions on the topic in SE but none seem to satisfy me.So,the question is as follows:1)What is the relation between thermodynamic equilibrium and statistical equilibrium ...
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### Chemical equilibrium for distinguishable reactant particles

Denote the partition function of a single particle by $\zeta$. The particles of one type of reactant in a chemical reaction are normally indistinguishable. The partition function of $n$ number of a ...
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### Direction of the normal force [closed]

Suppose we have a bar with non-zero mass inside a hemispherical bucket fixed to the ground. Suppose, too, that there is friction between the bar and the inner spherical surface of the bucket. Part of ...
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### When calculating Lagrange points, $L_3$, $L_4$ and $L_5$ are good, but why are my $L_1$ and $L_2$ too close to the Earth?

I'm using python to calculate the Lagrange points of the Sun-Earth system. I started assuming that - for $L_1$ at least - the sum of the gravitational acceleration towards the Sun and the centripetal ...
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### Is bouncing ball (100% collision) an oscillatory motion/SHM or both or none?

My teacher told me bouncing ball (100% elastic) is oscillatory motion that does not have a stable equilibrium position and restoring force. It is just to and fro motion and thus called oscillatory ...
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### How to calculate equilibrium time for a communicating vessel with height difference?

The scenario is that a communicating vessel or a U tube without lids is filled with water. There is a height difference between the two pipes of this tube. Then there will be hydraulic pressure and ...
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### Can a body be in thermal equilibrium at a different temperature from surroundings?

As per my knowledge bodies attain constant temperature (thermal equilibrium with surroundings) when they absorb and emit energy at equal rates. Let us say temperature of surroundings is T1. We have a ...
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### How are curved soap films stable?

How do curved soap films remain in equilibrium, if surface tension tries to pull them taut? What I understand: Surface tension acts tangentially on a surface. The potential is energy is proportional ...
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### Whether there is an isolated system, it will enter equilibrium [duplicate]

For a thermodynamically isolated system, will it eventually move toward thermal equilibrium? Will there be exceptions to the system?
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