Questions tagged [models]

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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10 views

What exactly is the framework (or model) in which Electromotive Force is a meaningful quantity?

As far as I understand, there are two definitions of "Electromotive Force", one being the integral of a non-conservative (non-dissipative) force per unit charge acting on electrons along a path in a ...
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11answers
7k views

Can mathematics lead to a result which is physically untenable?

Consider some known physical fact, e.g. $\nabla \cdot \mathbf B = 0$ for the magnetic induction $\mathbf B$. Now, is it possible that a mathematical theorem exists, which yields a wrong prediction? ...
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13 views

Are there analytical solutions for systems involving self-inductance and mutual inductance between two coils?

I have a real physical system where I have a moving coil inducing in a conductive (non-laminated) metal core. So I decided to model it, at each position, as being a system of 2 coils, one coil being ...
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2answers
31 views

How is the transition from kinetic to static friction modeled?

There are tons of information about the transition from static friction to kinetic friction but I'm having a little trouble finding information about the converse situation. I need that because I'm ...
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22 views

Model for ice sheet thickness [closed]

How should I proceed to find a formula $\lambda(t)$ for the thickness of and ice sheet in terms of The diference $T_{a}(t)-T_w(t)$ of the temperatures of air above the sheet and water below Thermal ...
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1answer
34 views

Correlations vs. negligence of correlations in covariance matrix

Suppose I have a model composed of two parameters $(a,b)$ that I want to describe a set of data points with. In CASE A, I fit the model taking into consideration the correlations between the data ...
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4answers
2k views

Are laws of nature absolute or are they just very good approximations? [closed]

Newton's second law, for example, states that $F=ma$. Is this absolutely true, down to the smallest possible unit of measurement? Or is it just a handy approximation that happens to work extremely ...
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2answers
52 views

Changing derivative to difference quotient

Can differential be changed to Delta or difference? In high school education, in the acceleration section of Newton's formula 2, acceleration is a change velocity (velocity difference) divided by a ...
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2answers
282 views

How can integration be used in deriving radioactive decay formula?

I recently learnt the derivation of radioactive decay formula and I am quite surprised about using integration to derive the formula. But $N$ (the number of atoms) can only be discrete numbers (like ...
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0answers
23 views

Model fit error pinching

I am performing a model function fit, $f=f(x,a,b)$, with the two parameters $\left\{a,b\right\}$ to be determined from the best fit to a set of data. In my determination of the resulting $1 \sigma$ ...
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1answer
44 views

What next after Niels Bohr's model? [closed]

I'm in 9th grade,so I know Bohr's model. But it has many demerits: 1) It is against Heisenberg’s uncertainty principle 2) It cannot explain Zeeman and stark effect 3) No justification for his ...
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27 views

Neutrino flavor models from irreducible representations of discrete groups [duplicate]

I am starting ph.D in neutrino physics-ph. I've read some papers on discrete symmetries and neutrino mass models. Neutrino flavor models are built using irreducible representations of discrete groups, ...
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31 views

Could uncertainty principle be considered a purely epistemological device?

I am trying to wrap my head around the basics of quantum theory and was wondering if my conclusions are reasonable. From what I understand, as far as quantum theory can be applied, it considers all, ...
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0answers
28 views

Is it possible to model calories burned using mass of the human, avg velocity and time travelled

I know it's impossible to get the exact value of calorie burned but a heuristic or an approximation would be just enough. Given human body is 70% efficient then calorie burned=3.33*energy dissipated
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45 views

Modelling a full 360º rotation with a swing using a pendulum

Kay so basically I modelled the Kiiking sport ( which consits on swinging on a stiff-rodded swing till you can reach the top and do the full swing ) using a change to polars $ (r,\theta) $ in the y-...
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1answer
103 views

Einstein Field equations for the whole universe

Can someone please show the EFE solved for the entire universe. I've heard people say that 'Einstein solved the Einstein equations for the universe and found this'. If I am missing something, what ...
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2answers
81 views

What is the mathematical expression of the Lambda-CDM model?

The conceptual meaning of this model is clear to me. But where can I find the actual mathematical model? The Wikipedia page says "The simple ΛCDM model is based on six parameters". Six parameter ...
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1answer
38 views

Mechanical-electrical analogies

From wikipedia: In the impedance analogy, for instance, this results in force and velocity being analogous to voltage and current respectively. claim: current is analogous to force logic: the unit ...
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5answers
143 views

Are there good examples of entities that are taken to exist in physics because talking about them is useful, but that don't really exist? [closed]

This question is for work in philosophy, but can only answered by physicists. It's hard to make it more precise without already knowing the answer to it. I'm looking for a good example, if there is ...
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0answers
51 views

A Physics Book for Experimental Evidence

I have come to notice how Physics is developed: we do some experiments and (from them) draw concise conclusions, which we call physical laws. Then we come up with the appropriate mathematics to—fully ...
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4answers
148 views

Philosophy of Science: Do electrons exist, or are they just models to explain physical phenomena? [closed]

I didn't find any SE site for "Philosophy of Science" hence I am asking it on Physics SE because it is related to Physics more than to Philosophy. As law of gravitation is a model which was proposed ...
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3answers
70 views

What is the necessity to universalise a law? [closed]

What are the necessary conditions or observations that are required for universalisation of a law? I am not good at English so by universalise I mean to claim something to be universal. So how can ...
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2answers
84 views

What species of arguments are used in physics and science in general? [closed]

Arguments are needed to provide theories but I'm only used to deductive reasoning in physics and science, maybe due to their empirical nature. Does anyone know if other species of arguments have or ...
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1answer
32 views

Is an epoch-based approach valid for modeling $N$-body systems?

Consider a 3-body Newtonian system with equal masses such that velocity change at a given time epoch for a single body is given by: I am interpreting that if $\vec{R_2}$ and $\vec{R_3}$ also change ...
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0answers
30 views

What is the mathematical approximation for uniform gravitational field in Newtonian Mechanics? [duplicate]

When measuring the local gravitational field using a simple pendulum, one of the core assumptions is that the gravitational field is homogeneous. But the theory itself (Classical/Newtonian Mechanics) ...
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1answer
122 views

Rigid body dynamics: modelling a polygon bounce off ground

I'm currently making a physics simulator, but I'm having some trouble making a polygon bounce off the floor. I know that collisions are normally modeled as described below by ja72, but I did it ...
2
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2answers
74 views

Can gravitational waves be visualized in the elastic rubber sheet model of gravity?

To visualize the space curvature related to gravity, there is a model or analogy using an elastic sheet and a weight. A rubber sheet is spanned like a very soft trampoline, and a heavy ball on it ...
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1answer
41 views

A doubt regarding Modelling physical phenomena and position uncertainty

For example, in velocity, when we say $v=\frac{dx}{dt}$, there is no proof for it. Its almost like an axiom. Something taken to be true, without a proof. How do I know that for every $x=f(t)$, $v=f'(t)...
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2answers
286 views

Why Bohr atom model is still being tought in high school? [duplicate]

Bohr atom model is still the textbook content of today's high school physics. We all know that the Bohr model is only suitable for single electron hydrogen atom, not suitable for other atoms. For ...
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1answer
289 views

Mathematical Model for a Pendulum in an Electric Field

I am studying Higher Level Physics and for my Physics IA I am doing an experiment determining the effect of the voltage between two parallel plates on the on the frequency of a pendulum in between the ...
3
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2answers
160 views

Why cube roots or in general $(2n-1)$th roots are rarely seen in equations in physics?

I rarely saw any equation in physics which involved cube roots or odd roots.Even while solving problems I rarely saw any odd root or cube root. So why nature prefers even powers of physical ...
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0answers
48 views

Are conservation of mass and conservation of energy *independent* constraints for physical systems?

I'm modeling fluid systems and want to use conservation of mass (aka 'continuity') and conservation of energy as constraints to help solve for certain system parameters. But it occurred to me that the ...
4
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1answer
322 views

Do we give a mathematical structure to the system or to its representation?

My professors taught me that in physics you have to make a mathematical representation of the physical system. Depending on what type of physics you are working on, the mathematical models change. I ...
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0answers
16 views

Viscoplastic Anand Model of Solder Alloy

I have found some data of viscoplastic Anand model for the SAC305 solder joint of electronic devices in the literature. Does this data depend on the thickness, length and width of the joint? I mean ...
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2answers
112 views

Formal name for the “pianology” objection towards contemporary particle physics direction of research?

In a popular science book, an interesting objection towards the current direction of particle physics was stated. I tried to search for more on this, but got nowhere. Since I assume this is not an ...
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1answer
35 views

How to model mass diffusion with half life

I am in the process of writing a model for the diffusion of a chemical in an aqueous medium. Typically, to do this, one would use the diffusion equation $$\frac{\partial}{\partial t}U=\gamma \nabla ^...
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1answer
26 views

Can classical thermic agitation modeled using QM?

A number of people has considered probability clouds as the sign there was hidden variables determining actual motion and always definite positions of particles, as a thermal agitation. This question ...
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0answers
51 views

Is Universal Law of Gravitation a 'law'? [duplicate]

My textbook mentions that the universal law of gravitation cannot be proved. If so, then why is it called a 'law' and not a 'hypothesis'?
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5answers
4k views

What does it mean that physics no longer uses mechanical models to describe phenomena?

I've just started reading Sommerfeld's Lecture on Mechanics, with no background in physics (only in math). Can you explain to me what the author means with the bold sentence? Mechanics is the ...
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6answers
6k views

Do working physicists consider Newtonian mechanics to be “falsified”?

In the comments for the question Falsification in Math vs Science, a dispute around the question of "Have Newtonian Mechanics been falsified?" That's a bit of a vague question, so attempting to ...
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0answers
18 views

Rutherford's and Bohr's model of atom [duplicate]

Rutherford's model of atom was ruled out because it failed in explaining stability of an atom. Since any particle that is accelerating continuously emit radiation. And in case of an atom eventually ...
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0answers
59 views

Spontanous emission Hamiltonian model

I am looking for a clear (and not too long) model of spontaneous emission, for an atom modeled by a two level system in a cavity where the field is multimode I am looking for model bases on ...
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1answer
121 views

Time evolution of molecular signal from a laser-induced plasma - finding the right model for my data

I am looking at molecular emissions in laser-induced plasma plumes created in argon at reduced pressure (in the mbar range). To be precise, these are heteronuclear diatomic molecules that emit ...
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2answers
106 views

Can we create new physics through moderately brute force computing? [closed]

So my argument for this is that the expansion of knowledge in any field of physics depends on what is previously known, and what we physicists express or knowledge as equations. So here's what I ...
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1answer
49 views

Modeling heat transfer of a long pipeline with heated fluid and flow as a lumped system with time delay

I want to model the heat transfer of a very long pipeline and how heated fluid is flowing through this system. It is possible to model this system as a distributed system. However I want to model this ...
2
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1answer
184 views

How to test quantum mechanics?

In this paper, Testing quantum mechanics, S. Weinberg states that The problem is to know what to test. Usually we can get guidance on how to test a theory like general relativity or the standard ...
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1answer
36 views

What are the assumptions for porous media to be considered as continuum?

The poroelastic models like - Biot theory- are built on the continuum approach. But I am not able to understand, how this heterogeneous media can be considered as a continuum. However, If the porous ...
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6answers
4k views

Why exactly are singularities avoided or “deleted” in physics?

What is the real reason that make us reject singularities everytime we see them in a theory/model? For example, in GR, it is predicted that black holes singularities have infinite density. This makes ...
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3answers
50 views

Finding the equations of motion with observations

Let's say that we don't know the equations of motion. I will try to predict where my ball will fall when I shoot it with an angle $\alpha$ and and speed $v$ by finding the function that describe this....
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0answers
60 views

High-energy effective field theory

Usually when one speaks of effective field theories, one is looking to integrate out certain fields which are typically heavy in comparison to the regime of interest. That is one has a theory at a ...

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