DO NOT USE THIS TAG just because the involved physics is based on a model. All physics descriptions are inherently model-based. This tag is reserved specifically for addressing model development, validity, simplification, or other meta-model questions.

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0answers
33 views

model for flexible stick

I'm trying to model a flexible stick with a partial differential equation. I want one of the ends to be fixed and the other end to swing. Do you guys know of any good models I can use? Any ...
2
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1answer
106 views

Identifying an optics equation in a code refactoring project

I apologise if this a somewhat naive post. My knowledge of optics is limited, and I am learning on the job, so to speak. I'm a computational biologist, dabbling in a bit of physics. I'm currently ...
2
votes
2answers
200 views

Sampling a distribution (from a galaxy model)

I am reading the following article: http://www.kof.zcu.cz/st/dis/schwarzmeier/galaxy_models.html and am currently at section 5.6 (positions of bodies in a galaxy). I am trying to redo the simulations ...
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2answers
2k views

Why would an electron in an orbit be accelerating continuously and would thus radiate away its energy and fall into the nucleus in a classical model? [duplicate]

I was reading this answer by madame anna v: You are right, the planetary model of the atom does not make sense when one considers the electromagnetic forces involved. The electron in an orbit is ...
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2answers
190 views

The nature of theoretical models

Mathematics is exact. It is a beautiful language that allows us to express quantities that aren't possible to be represented physically. We build theoretical models of physical systems that work out ...
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0answers
40 views

Which model of computation can be viewed as being extended by the currently most relevant models of quantum computation?

Which model of quantum computation resembles most closely the attempts of implementation currently being made? And which non-quantum model of computation is the conceptually closest one to the above ...
2
votes
1answer
103 views

Can all theories of theoretical physics be generalized to any (arbitrary) number of dimensions?

Please explain from: mathematical point of view "laws of mathematics", and, physical point of view "laws of physics"? Or is there any bound on number of dimensions?
-1
votes
1answer
112 views

How can we depend on the mathematical axioms that break down at the nano-level? [duplicate]

Mathematics "makes sense" at our scope of view. For example, gravity seems to obey the fact that it accelerates at a rate of 9.8 meters a second^2. However, when an object drops, the force of gravity ...
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7answers
528 views

Macroscopic laws which haven't been derived from microscopic laws

Can you think of examples where a macroscopic law coexists with a fully known microscopic law, but the former hasn't been derived from the latter (yet)? Or maybe a rule of thumb, which works but ...
5
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1answer
540 views

't Hooft for laypersons

I have looked at some of 't Hooft's recent papers and, unfortunately, they are well beyond my current level of comprehension. The same holds for the discussions that took place on this website. (See, ...
86
votes
7answers
11k views

Why do people categorically dismiss some simple quantum models?

Deterministic models. Clarification of the question: The problem with these blogs is that people are inclined to start yelling at each other. (I admit, I got infected and it's difficult not to raise ...
1
vote
1answer
188 views

How can I validate a numerical model using an analytical solution of the same scenario?

In the course of my research project I have been tasked with validating an acoustic model, however I am having trouble conceptualising what I am supposed to do. I have found an analytical solution for ...
1
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1answer
233 views

Fitting a circuit scheme to a simpler model

I have to simulate the electric field within a gas filled discharge gap generated by a radio frequency voltage generator. The circuit, provided to me by the experimenters somewhat far away, is given ...
1
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2answers
85 views

Any noise slowly starting to take effects?

I am studying a system subject to random noise, or a system driven by some noise, for example, heat flow or wave propagation perturbed by noise. I would like to know if there is a real system where ...
0
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0answers
139 views

What's the physical interpretation of constants in Laplace equation and diffusion equation?

What's the physical interpretation of constants in wave equation and diffusion equation? $$u_{tt}=c^2u_{xx},$$ $$u_{t}=ku_{xx}.$$ Please introduce some reference about mathematical modeling of ...
0
votes
1answer
502 views

Eddy current losses in electric steel by harmonics of a magnetic field

I am working on an model of a permanent magnet synchronous machine. Right now I am stuck with calculating the eddy current losses caused by the harmonics of the stator magnetic field in the electrical ...
2
votes
1answer
722 views

Is energy always proportional to frequency?

Google has no results found for "energy not proportional to frequency" and many results for E=hf. Is there an example of an energy that is not proportional to frequency?
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2answers
428 views

Does a scale model with 1/2 the linear length have 1/8 the mass?

If a scale model has 0.5x the original length in all directions, should its mass be 1/8th of the original mass?
2
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0answers
173 views

Turboshaft Turbine Mathematical Model

Are there any simplified mathematical models for how two gas coupled turbines (also called a free power turbine) should interact with one another as the speed of the driving turbine changes. (i.e.) ...
1
vote
1answer
81 views

If a cart hits a wall, does the weight of it affect how it moves, when the center of gravity is constant?

I have a model that represents a bicycle (a wood block with wheels), and I'm balancing the center of gravity so it's the same as a real bike. However, when the center of mass is kept constant, does ...
2
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0answers
75 views

Elimination of the node

Recently I have been reading a lot of astronomy papers on reductions in models of the solar system. A reoccurring concept is the elimination of the node. However, they never explain what the node is ...
1
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1answer
977 views

Definition of elementary particle [duplicate]

Possible Duplicate: Why are atoms particles? According to wikipedia an elementary particle or fundamental particle is a particle not known to have substructure. Moreover, I've learned ...
1
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0answers
58 views

Modeling the probability of a photodiode measuring photons targets at a neighbor

In current digital cameras, sensors are arrays of photodiodes which "transform" photons energy to electrons. I am aware that the probability of a photon to generate an electron is modeled by a Poisson ...
2
votes
4answers
220 views

What is the simplest system that has both, discontinous and continous phase transitions?

I am looking the simplest system that has both discontinous phase transition and a continous phase transition between the same phases (you can change one parameter). discontinous transition: first ...
4
votes
3answers
492 views

Can anyone estimate what proportion of water remains after I flush a toilet?

Imagine I have a clean toilet with some amount of water in the bowl. When I flush the toilet much of that water will be displaced by the tank's water. I want to work out (or model really) what amount ...
3
votes
0answers
530 views

Is there any simple quantum model by Gerard 't Hooft which can explain the double slit experiment?

This question is directed to Prof. 't Hooft and anybody who is familiar with his papers. It is a reaction to Prof. 't Hooft's question why nobody is excited about his classical models for quantum ...
3
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2answers
131 views

A problem of approximation [duplicate]

Possible Duplicate: Why are continuum fluid mechanics accurate when constituents are discrete objects of finite size? When we apply differentiation on charge being conducted with respect to ...
3
votes
4answers
4k views

Bohr's model of an atom doesn't seem to have overcome the drawback of Rutherford's model

We, as high school students have been taught that-because Bohr's model of an atom assigns specific orbits for electrons-that it is better than Rutherford's model. But what Rutherford failed to explain ...
3
votes
4answers
434 views

Formulation of general relativity

EDIT: I think I can pinpoint my confusion a bit better. Here comes my updated question (I'm not sure what the standard way of doing things is - please let me know if I should delete the old version). ...
3
votes
2answers
295 views

Relating the power to weather variables [closed]

Could you please help me in this problem? I have 3 independent variables, (T,H,t) , as inputs and one output P ( I have all data for these inputs and the output, done experimentally measured every ...
5
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0answers
702 views

Interpretation of Stiffness Matrix and Mass Matrix in Finite Element Method

I would like to have a general interpretation of the coefficients of the stiffness matrix that appears in FEM. For instance if we are solving a linear elasticity problem and we modelize the relation ...
3
votes
1answer
112 views

Are there microscopic theories, which work, but which wrongly predict macroscopic behaviour?

Motivated by this question (and the P. W. Anderson article linked in that question, which I came across here somewhere today and just read) I wonder about something, which is somewhat bordering an ...
4
votes
1answer
590 views

The most challenging physical phenomena [closed]

What are examples of endeavors, in the history of mankind, to understand physical phenomena with models which were proved to be incorrect later, reformed significantly, or are still under ...
1
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0answers
236 views

Modeling the trajectory of a particle in an Electric field [closed]

[This problem has been resolved, sorry for posting in the wrong forum!] (I was trying to model the trajectory of a particle in an electric field.)
4
votes
1answer
195 views

Event-by-Event Simulation of Quantum Phenomena

I just recently stumbled over http://rugth30.phys.rug.nl/dlm/ and http://www.sbfisica.org.br/bjp/files/v38_26.pdf As the title suggests these are presentations of mathematical models capable of ...
3
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0answers
244 views

Simple model of the solar system. Parameters? Accuracy?

I was thinking of making a simple 2D model of the solar system, with planets moving along ellipses like $$x(t) = k_x \sin(t + k_t) (\sin(k_\phi) + \cos(k_\phi))$$ $$y(t) = k_y \cos(t + k_t) ...
4
votes
2answers
966 views

Why are continuum fluid mechanics accurate when constituents are discrete objects of finite size?

Suppose we view fluids classically, i.e., as a collection of molecules (with some finite size) interacting via e&m and gravitational forces. Presumably we model fluids as continuous objects that ...
4
votes
3answers
325 views

Guessing what a simple partial differential equation is describing physically

Is there an easy way to look at a partial different equation and get a sense of what kind of phenomena it is physically describing? I have an equation that looks like this: ...
1
vote
1answer
159 views

SDE for particle, PDE for the density

Given a particle on the plane we can assume that it follows 2D Brownian motion. On the other hand if there is a lot of such a Brownian particles one can be interested in the evolution of the density ...
2
votes
2answers
540 views

Software for simulating 3D Newtonian dynamics of simple geometric objects (with force fields)

I'm looking for something short of a molecular dynamics package, where I can build up simple geometric shapes with flexible linkages/etc and simulate the consequences of electrostatic repulsion ...
2
votes
2answers
282 views

Is it meaningful to imagine a sphere uniformly charged with 2e?

If the charge is large, considering charge density is usually meaningful despite the discrete nature of electrical charge. The following sentence is part of a problem in a textbook on ...
3
votes
1answer
309 views

Olympic games and the local g

As you probably know, the two next Olympic games will take place in London and Rio. Randall, author of xkcd, did an interesting observation (that I had never thought of) in http://xkcd.com/852/ , ...
2
votes
1answer
411 views

Modelling noise with distance

I was wondering about the relation between noise with distance, assuming a point source, using sound as the method for communication and air as the medium of communication. Obviously as the distance ...
3
votes
2answers
1k views

Approximating mean daily and hourly temperature beyond Fourier series

Summary: What "well-known" and short parametrized mathematical function describes daily and hourly temperature for a given location? If you look at the mean daily temperature graph for a given ...
0
votes
1answer
516 views

How to model the dynamics of human movement?

I am trying to derive a state space equation for human movement (i.e. walking, running, standing still) in some normal distribution sense. The following equations should not be so hard to follow: If ...
8
votes
2answers
631 views

Do current models of particle physics explain the chemical properties of elements/compounds?

I have a particle system of seven protons and seven (or sometimes eight) neutrons (each formed by their appropriate quarks, etc.) bound together in a state that can be macroscopically described as a ...
0
votes
1answer
140 views

Computing delta temperature based on radiation and heat loss

Is there a formula that gives me the instantaneous change in temperature under ideal circumstances? Details: On a cloudless day, temperature is affected by two major things(?): While the Sun is ...