# 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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### 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 ...
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? ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 $1 \sigma$ ...
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 ...
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, ...
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, ...
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
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-...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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) ...
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 ...
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 ...