# Questions tagged [equilibrium]

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### Forces acting on an orange placed on a table in equilibrium [closed]

An orange sits on a table in equilibrium. What forces are acting on it? What is the reaction force to each of the forces acting on it? What are the action and reaction pair?
1answer
154 views

### How “Eyeball Glide Ball” toy works?

How this toy works? As you roll the ball on the table, the eye always point up: (original video source: https://youtu.be/_3kAjWaxM30) As far I am aware, no magnets are involved in the construction ...
3answers
165 views

### Why is boiling a non-equilibrium process? [closed]

Boiling is a non-equilibrium process. Which equilibrium (mechanical, chemical and thermal) are not maintained during boiling and why?
4answers
645 views

### Can a positively charged conductor have negative surface charge density somewhere?

This is a simple question that occurred to me while thinking about electrostatics. Let's consider a positively charged isolated conductor in equilibrium. In general, the surface charge density varies ...
2answers
349 views

### Why is the restoring force not zero at the equilibrium position of simple harmonic motion?

The restoring force is applied in order to take the body it's equilibrium. Then in a SHM why in the mean position restoring force maximum rather than being zero as it has reached equilibrium. (After ...
2answers
558 views

### Beam attached to a wall

Suppose I have a rigid beam attached to a wall, how can the reaction force on the point the beam is attached to generate a static equilibrium on the beam? ...
0answers
483 views

### Can a substance have zero vapour pressure above absolute zero?

According to this Reddit thread, the answer is no, vapor pressure can't be zero when temperature is above absolute zero. I suspect the answer might actually be yes according to a precise definition I ...
1answer
57 views

### Lagrange points and gravity

I have just found an article talking about the L1 to L5 equilibrium positions of gravitation around stars, planets, etc. As far as I could learn from this website and other research I have done the ...
0answers
46 views

### Is there an open quantum system analogue of the equilibration time bounds for classical ergodic Markov chains?

Background For classical ergodic discrete Markov chains, we can bound the time taken to reach the stationary distribution to the spectral properties of the transition matrix. I will outline this ...
1answer
115 views

### Why does the gas in Sun's outer layer not expand?

Since in the outer part of sun it consists gases. Why don't the gases expand due to heat? This was asked by my friend. And he said that the gases are attracted by the plasma layer by a force. So the ...
1answer
137 views

### What happend to the tension? [closed]

If crane with uniform arm raised by shortening cable,what is the effect to the tension of the cable?I know the tension will increase but what cause? Bcs of increasing in angle?Or got thing with torque?...
2answers
987 views

### Can a body be in equilibrium when only one force acts on the body? [duplicate]

I think that when we throw a body in air, at top point the body is in equilibrium but gravitational force is still acting. Is this correct?
1answer
57 views

### Defining a 'small disturbance which dampens in time' while identifying stable points in a nonlinear system

I'm reading the book "Nonlinear dynamics and Chaos" by S Strogatz. In section 2.2, titled "Fixed points and stability", he defines equilibrium points as solutions where ...all sufficiently small ...
0answers
27 views

### In terms of the greenhouse effect, what is the Earth's heat capacity?

Has the earth’s atmosphere reached an equilibrium at which the input radiation energy roughly equals its output, or is the output significantly lower than the input because the energy is being used to ...
2answers
107 views

### Electric charge and net force [closed]

Consider two point charges $+Q$ and $-Q$, which are fixed a distance $d$ apart. Can you find a location where a third positive charge $Q$ could be placed so that the net electric force on this third ...
1answer
52 views

### free stress boundary condition

I would like to understand better the free stress boundary condition. Indeed, force equilibrium writes $\nabla.\sigma=0$, and not $\sigma=0$, so which basic physical principle (such as force ...
1answer
72 views

1answer
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### Relation between ergodic hypothesis and fundamental postulate of statistical mechanics?

The fundamental postulate states, roughly, that each microstate of a system consistent with certain known constraints (e.g. on the total energy of the system), is equally likely to occur. The ...
2answers
89 views

### Can we take rotational equilibrium of only one part of a body?

Can we take rotational equilibrium of only one part of a body? Such as in a step ladder, where BD is a rope. Can we take rotational equilibrium of AC about C, and not the full ladder?
3answers
60 views

### How is equilibrium possible here? (motor + linkage)

During my engineering course we were discussing systems in equilibrium and I came up with a situation that I don't understand. Say we have an electric motor which drives a linkage consisting of 'disc ...
2answers
1k views

### How does a balancing toy work?

I know that the balancing toys have their center of mass under the axis on which they are balancing. That's why they stay still. But when we give a little tap on it, it re-balances itself. But how ...
2answers
144 views

### Clarification about Thermodynamic Equilibrium

Let’s say that we have a big sphere filled with gas, and in its center a solid core of a very dense material. The sphere is in equilibrium, alone in space. Because of the gravity of the core the gas ...
0answers
162 views

### Is there any example of a real-life system which violates the “third law” of thermodynamics while remaining at equilibrium?

I assume the following statement for the "third law" of thermodynamics: $$\lim_{N \to \infty} \lim_{T \to 0} \frac{S}{N} = 0 \tag{1}\label{1}$$ That is to say, I am considering those systems with a ...
1answer
535 views

### Prevost Theory of Exchange

I am having a trouble in understanding this concept. If bodies are at thermal equilibrium, there is no heat transfer. Heat is transferred through three different ways: Conduction, convection and ...