# What is Isolated system: Definition and 45 Discussions

In physical science, an isolated system is either of the following:

a physical system so far removed from other systems that it does not interact with them.
a thermodynamic system enclosed by rigid immovable walls through which neither mass nor energy can pass.Though subject internally to its own gravity, an isolated system is usually taken to be outside the reach of external gravitational and other long-range forces.
This can be contrasted with what (in the more common terminology used in thermodynamics) is called a closed system, being enclosed by selective walls through which energy can pass as heat or work, but not matter; and with an open system, which both matter and energy can enter or exit, though it may have variously impermeable walls in parts of its boundaries.
An isolated system obeys the conservation law that its total energy–mass stays constant. Most often, in thermodynamics, mass and energy are treated as separately conserved.
Because of the requirement of enclosure, and the near ubiquity of gravity, strictly and ideally isolated systems do not actually occur in experiments or in nature. Though very useful, they are strictly hypothetical.Classical thermodynamics is usually presented as postulating the existence of isolated systems. It is also usually presented as the fruit of experience. Obviously, no experience has been reported of an ideally isolated system.
It is, however, the fruit of experience that some physical systems, including isolated ones, do seem to reach their own states of internal thermodynamic equilibrium. Classical thermodynamics postulates the existence of systems in their own states of internal thermodynamic equilibrium. This postulate is a very useful idealization.
In the attempt to explain the idea of a gradual approach to thermodynamic equilibrium after a thermodynamic operation, with entropy increasing according to the second law of thermodynamics, Boltzmann’s H-theorem used equations, which assumed a system (for example, a gas) was isolated. That is, all the mechanical degrees of freedom could be specified, treating the enclosing walls simply as mirror boundary conditions. This led to Loschmidt's paradox. If, however, the stochastic behavior of the molecules and thermal radiation in real enclosing walls is considered, then the system is in effect in a heat bath. Then Boltzmann’s assumption of molecular chaos can be justified.
The concept of an isolated system can serve as a useful model approximating many real-world situations. It is an acceptable idealization used in constructing mathematical models of certain natural phenomena; e.g., the planets in the Solar System, and the proton and electron in a hydrogen atom are often treated as isolated systems. But, from time to time, a hydrogen atom will interact with electromagnetic radiation and go to an excited state.
Sometimes people speculate about "isolation" for the universe as a whole, but the meaning of such speculation is doubtful.

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1. ### Mixing two gases in an isolated system and calculating final p and T

Hey everyone, I have an attempt at fully solving this problem (my final pressure is ##p_f = 5373,64 hPa##, final temp. is ##T_f = 303,15K = 30C##), but this exercise confuses me very much. First, I have not used the masses in my calculations and I'm pretty sure my prof. accidentally copypasted...
2. ### Confusion about the difference between isolated and non isolated systems

Read the book and conducted research on the internet. Came to conclusion that this was an isolated system because the girl was being accelerated by gravity but answer is non isolated. Can someone please help me grasp this concept better.
3. ### I Total energy of an isolated system

If a closed system has kinetic and potential energy such as the total energy (the sum of the two) equals zero for all times, what does that mean? In other words, what does it physically mean that the total energy is always zero for a closed system? I think I have a small misunderstanding of the...
4. ### Change in Entropy for an isolated system

ΔU_A + ΔU_B = 0 (Is this because of isolated system am I right?) ΔU_A = CA * (T_final - T_A ) ΔU_B=CB * (T_final-T_B) And because of a very slow process : S=ln(T) T_final= (CA T_A + CB T_B)/(CA + CB) ΔS_final = CA*ln(T_f/TA) + ln(T_f/TB) * CB My QUESTION is : When we say No heat exchange...
5. ### Choosing the isolated system

I have difficulty at choosing isolated system.We can not choose rope and block to be the isolated system?This is for number 20.
6. ### I The Universe as an isolated system

Can the universe be treated as a thermodynamic isolated system? And why?
7. ### How is the 2nd law of thermodynamics obeyed in this system?

Imagine there is an radiation concentrator (winston cone) surrounded with extremely many layers of foil for radiation insulation, except at the smaller opening. Every part of the setup is initially in thermal equilibrium with the surroundings. The amount of thermal radiation flowing through the...
8. ### Why there is a " > " sign in the entropy of an isolated system

it seems it is not reasonable Sorry it said that delta S>=0 in an isolated system. i know why they put " = " sign, but i don't know why it is still possible that dS>0 in an isolated systembecause in an isolated system,it is said that dQ=0 (because no heat transfer between the system and the...
9. ### Heat exchange in an isolated system

Homework Statement In a container of negligible mass, equal amounts (in weight) of ice at 0°C and steam at 100°C are mixed at atmospheric pressure. Assuming no heat exchange with the surroundings, what is the temperature when the system reaches equilibrium? What are the fractions of weights of...
10. ### Work: Isolated & Non-Isolated Systems Difference

Okay, so I've reached the Work Chapters in my textbook, and I've noticed some contradictions, especially in what consists (and what doesn't) an Isolated System, plus the external and/or applied forces. For example, in one of the "Speed Questions" it categorizes a single cube as a non-isolated...
11. ### Law of conservation of momentum in a non isolated system.

Is the law of conservation of momentum valid in non isolated system . What is an isolated system? My teacher confuses me that the law is valid in an non isolated system . They even say that when we say about the isolated system (meaning they are present ) we do not consider the air resistance...
12. ### Entropy in an isolated system

Hello, In my textbook I read this example: A gas in an isolated system expands after pulling out a separating plate, so its volume increases and there is no work or heat exchange. the entropy of if the ideal gas is $$\Delta S = n R \ln \frac {V_1} {V_2}$$ and the second law of thermodynamics...
13. ### Momentum and isolated systems

This is with regard to 2 boxes of different masses that are stacked on top of each other and pushed at a constant velocity across a table that has friction. One of the sentences is right: "When the boxes move at a constant speed, there is no change in momentum. This means that the boxes are an...
14. ### Can the work in a isochoric process be non zero?

I came up with a doubt regarding isochoric irreversible processes. Is it always true that, for any isochoric process, reversible or not, the work exchanged by the system is zero and the heat exchanged is ##Q=\Delta U##? I'm asking this because, in a exercise on thermodynamics trasformations of...
15. ### How to check if frame is inertial?

inertial frame is one in which isolated particle has constant velocity but is there actually any "isolated particle " ? how then can frame be defined as or not being inertial ? or is it that - for a system in which acceleration due to external forces is equal for all members , the frame of...
16. ### Is it possible to construct a thermally isolated system?

If I'm just trying to design a system to minimize heat loss, would the following suffice? The system or object would be magnetically levitated inside a vacuum chamber. The interior lining of the vacuum chamber would also be covered in a sheet of radiation reflecting material.
17. ### Thermally Isolated System

Homework Statement Consider a thermally isolated system consisting of two volumes, ##V_A = V## and ##V_B = 2V## of an ideal gas, separated by a thermally conducting and movable partition. The temperature of the gas in both sides are ##T_A = T_B = T##, and the pressures are ##p_A = p## and ##p_B...
18. ### I Schrodinger's cat, the multiverse and isolated systems

I know the debate about Schrodinger's cat is usually about things like consciousness but I want to talk about what it might say about isolated systems. Does the wave function of isolated systems remain in a superposition of observable states no matter how large the system gets? Say you have...
19. ### Question about movement in isolated system

I'm new to the forums and unfortunately I have a pretty dumb question... So in isolated system internal forces cancel each other out every single time,like pushing on a door of your car does not create any motion of your car at all. You basically can't pull yourself up by the bootstraps. I...
20. ### Why is the internal energy change of free expansion 0?

ΔU=q-w and in a free expansion w=0 and Free expansion is an irreversible process in which a gas expands into an insulated evacuated chamber. Does this mean that free expansion is an isolated system? Meaning the walls of the container are adiabatic in which no heat can enter the system and so q=0...
21. ### Question: Gravitational Potential Energy in a Ball-Earth-Moon system?

Hello, here's a questions I was wondering if any of you could solve. I don't have the exact numbers, but the scenario is this: a guy standing on the Earth throws a ball upwards and catches it a few seconds later. How does would affect the potential energy and/or mechanical energy of the...
22. ### Entropy of an isolated system

Homework Statement There is a line in a question: "Entropy of an isolated system is always maximised at equilibrium." And it is given true. But Why? Homework Equations None The Attempt at a Solution In an isolated system heat input is equal to zero. And we know that entropy= heat...
23. ### Poisson equation/zero padding and duplicating Green function

Hello, I need to solve the Poisson equation in gravitational case (for galaxy dynamics) with Green's function by applying Fast Fourier Transform. I don't understand the method used for an isolated system from (Hockney & Eastwood 1981); it says : I have 2 questions: * Why we duplicate the...
24. ### Water Pressure in an Isolated System

So I'm more into electricity, so fluids is not really a forte at all. But I have been thinking about this, and there must be some fundamental issue in the way that I view fluid pressure. Conditions: 1. I have a metal pipe, incompressible 2. There is water in the pipe, (incompressible? ...
25. ### Coffee cup, bomb calorimeter: Open, closed, or isolated?

Is a coffee cup usually considered to be a closed system? Why or why not? Does it matter that steam or hot coffee may be evaporating? (I think the steam is usually considered to be an insignificant amount of matter, allowing classification to be a closed system, but am unsure.) Is a bomb...
26. ### Kinetic and potential energy in firing a cannon

Homework Statement A 20.0 kg cannonball is fired from a cannon with a muzzle speed of 1000 m/s at an angle of 37.0° with the horizontal. A second ball is fired at an angle of 90.0°. (a) Use the isolated system model to find the maximum height reached by each ball. (b) What is the total...
27. ### Thermodynamics In An Isolated System

Hello, I was thinking about a situation last night and couldn't convince myself of a correct answer, so I thought i'd put it to you guys. Imagine an isolated system containing a star at some temperature radiating a given amount of energy into the environment. Can the environments temperature...
28. ### Changes in entropy of an isolated system

Homework Statement Consider two fixed volume bricks of mass m1=2kg and m2=1kg with initial temperatures T1=400K and T2=100K. They are enclosed in a system thermally isolated from the surroundings and are made from a material with a heat capacity cv = 1kJ/kg/K. A) In Process 1, the bricks are...
29. ### What is an isolated system ?

I have encountered 2 answers for this question. 1. In the natural sciences an isolated system is a physical system without any external exchange – neither matter nor energy can enter or exit, but can only move around inside. Truly isolated systems cannot exist in nature, other than possibly...
30. ### Gravity adding energy in an isolated system?

Disclaimer: I am not a physicist and this was just some random question that popped into my head. According to the law of conservation of energy, energy cannot be destroyed or created. So the energy in our current universe is the same as it was right after the big bang right? But can't...
31. ### How is energy of an isolated system defined ?

(energy is the capacity of a physical system to perform work and, an isolated system is a physical system without any external exchange – neither matter nor energy can enter or exit.) so, how is the energy of an isolated system defined? can it even be defined in principle??
32. ### What is the isolated system?

As we know the microcanonical ensemble is concerned with the isolated system. What is the definition of isolated system here? Can we call here each system which only is not in contact with any source of temeperature (No matter how much work is done) an isolated system?
33. ### Change in entropy in an isolated system

Homework Statement Derive an equation for the change in entropy that occurs in an isolated (micro-canonical) system containing N particles, if an adiabatic expansion from volume V1 to volume V1 takes place. Show that the number of microstates is given by V^N.Homework Equations Entropy S =...
34. ### Universe as isolated system

Does the current model of cosmology treat the universe as an isolated system?
35. ### Isolated System: Exploring Charge Conservation

"The charge of an isolated system is conserved" What is the meaning of isolated system ?
36. ### When will the entropy of universe(an isolated system) stop increasing?

Consider the universe as an isolated system, its entropy always increase? when stop? dS=>dq\T, as dq=o in universe an isolated system, dS always bigger than zero. so increase nonstop?
37. ### Entropy change in an isolated system

hi I am having a few conception problems with entropy problem: a solid with constant heat capacity and initial temp To, is brought in contact with hotter reservoir temp T1 and allowed to come into equilibrium. This is all isolated. a) is the change in the entropy of the universe negative...
38. ### Entropy to never decrease in an isolated system

I considered entropy to never decrease in an isolated system, so I am a little confused when i read about how molecules 'self assemble' to lower interfacial energy which leads to an ordering of the system... Is this ordering not a decrease in entropy violating the law that it always...
39. ### Gravitational Potential Energy of a Child in a Swing: Ropes Horizontal"

Homework Statement A 180 N child is in a swing that is attached to ropes 1.80 m long. Find the gravitational potential energy of the child-Earth system relative to the child's lowest position at the following times. (a) when the ropes are horizontal Homework Equations Kf+Ugf=Ki+U[SUB]gi[SUB]...
40. ### Potential Energy/ The Isolated system

Homework Statement A ball of mass m = 8 kg is dropped from rest at a height h = 13.9 m above the ground, as in Figure 7.4. Ignore air resistance. If the ball is being released with a downward speed 4.9 m/s initially, what will be its final speed when it hits the table 0.7 m below the release...
41. ### Question about mechanical energy in an isolated system

Hello, Consider a system that is made of a man and a hockey ball on ice (frictionless). Say the man's mass is 80kg and the ball is 0.5kg. At t=0, they are together and they don't move. At an instant the man throw the ball at \frac{10m}{s} against a wall (the ball suffers an elastic...
42. ### Why is the system not considered isolated in this scenario?

For the following question, the answer given is b. Non-Isolated http://tinyurl.com/2s3waq But may I know why it is not a. Isolated?
43. ### Maximum possible momentum change in isolated system

hello. If in isolated system two objects (one wih momentum 6 and the other with momentum 3)collide, total momentum of the system always remains the same (total_momentum=9). Depending on the mass, material of objects and some other variables, the change of momentum could vary. Does maximum...
44. ### Momentum and isolated system

hi,I already solved the problem but my question is partly related to it A person with mass m=80kg is climbing up the helicopter ladder that is hovering in the air.Person climbs with speed 0.5m/s relative to the ladder. With what speed is helicopter descending? If we think of helicopter...
45. ### Examining Probability and Isolated Systems in Physical Configurations

When we ascribe a probability to a physical configuration, are we not arbitrarily assuming 1. That the system excludes the observer, 2. How isolated the system is, 3. How comprehensive the system actually is, 4. The reproducibility of measurement?