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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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4answers
131 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
64 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
80 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
29 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) ...
2
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1answer
106 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
54 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
39 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
199 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 ...
0
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1answer
106 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
140 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 ...
2
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0answers
47 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
316 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 ...
0
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0answers
15 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 ...
1
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2answers
111 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 ...
1
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1answer
24 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
24 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
50 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'?
25
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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 ...
20
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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
16 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 ...
1
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0answers
52 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 ...
1
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1answer
117 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
101 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 ...
0
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1answer
46 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
174 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 ...
2
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1answer
32 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 ...
22
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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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0answers
23 views

Is this a simple fracture mechanics model

If I use the interatomic potential $V(x_i-x_j)= \frac{1}{2}k(x_i-x_j-a)^2$ for $|x_i-x_j-a|<b$ $V(x_i-x_j) = V_0$ for $|x_i-x_j-a|\geq b$ for the critical displacement $b$ and Equilibrium ...
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3answers
48 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
23 views

Aggregation phenomena : How to get from a discrete to a continuous point of view

I'm studying a diffusion limited aggregation phenomenon. The $N$ particles diffuse in a box and when there is a contact they stick with a probability $p$, and let's say to simplify $p=1$. Meaning that ...
0
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0answers
46 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 ...
0
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1answer
39 views

Application of linear constant coefficients ODE of the second order [closed]

I've asked this question in math forum. Apparently this question is not welcomed there. So maybe here I can get a proper response. Consider ODE in the form of $$y''+ay'+by=f(t)$$ where $a$ and $b$ are ...
1
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1answer
165 views

Laplace transform on thermodynamics equation

I'm trying to create a simple model of a single-flash geothermal plant which consist of 3 main parts (flash-separator, turbine, and condenser). Is there any way to create a transfer function using ...
3
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1answer
49 views

Theories, Corollaries, and Models

I apologize if this question seems overly basic. I was wondering how to recognize what a theory is really saying, as opposed to the explanation/corollaries that are drawn from it. As an example, take ...
1
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1answer
55 views

Numerically Modeling Coupled Oscillators Point Masses

I seek to model the motion of two coupled oscillating point masses as shown below: Note that x1(t) models the leftmost point mass and x2(t) is the motion of the rightmost point mass. I would like to ...
0
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2answers
89 views

Do we know, or at least have a strong argument for the fact that for a given time interval, we can always find a smaller time interval? [duplicate]

Motivation: In Biology, when, for example, biologists try to model the population dynamics of a population, they say: Let $N: \mathbb{R}^{nn} \to \mathbb{R}^{nn}$ be a function that represents ...
2
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0answers
28 views

Resource to learn modelisation of quantum measurement

I need to learn how we do model quantum measurement (for experiments for example). If we study a quantum system X, when we measure it we usually consider a projective measurement (so we use the ...
0
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1answer
36 views

How do we generalise a specialised case in physics?

I have come across this sort of thing a lot of times in my textbook. I give the examples below- Eg.1- In the case of a capacitor connected across an alternating current generator, we find $V_c=...
1
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1answer
357 views

If two different theories describe experimental observations equally well, can one be said to be more valid than the other? [closed]

Assuming both use accepted rules of logic, which of the two theories would be accepted and on what basis, for example: simplicity etc.
1
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1answer
80 views

Models in physics [closed]

As I said in another question I am just a physics enthusiast so I am sorry for my very poor knowledge. What is meant by models in physics? what is their function and why physicists imply them? Are ...
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9answers
4k views

How does a particle know how to behave? [duplicate]

How does a particle know it should behave in such and such manner? As a person, I can set mass is so and so, charge is so and so - then set up equation to solve its equation of motion but who ...
0
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1answer
76 views

Uncertainties in measurements and slopes

Suppose I have a mathematical model $y=mx$ and I have data for $x$ and $y$ and I want to fit the mathematical model on the data and determine the value of slope. I also have uncertainties of $x$ and $...
1
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2answers
122 views

Physical meaning of quantized energy of electron (or n=1,2,3…) in Bohr's model

To solve objections on Rutherford's model, one of which is energy deficit, Bohr postulated that the energy of the electron is quantized and $n=1,2,3...$ . But what does this postulate mean physically? ...
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14answers
2k views

How can the solutions to equations of motion be unique if it seems the same state can be arrived at through different histories?

Let's assume we have a container, a jar, a can or whatever, which has a hole at its end. If there were water inside, via a differential equation we could calculate the time by which the container is ...
0
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4answers
96 views

Mechanical Energy Analog to Capacitance

For starters I am a complete physics noob. I've been trying to understand basic fundamental ideas at a conceptual level I was drawn to the fact that work $(J) = FxD = CxV.$ I started trying to find ...
1
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1answer
69 views

From Bose-Hubbard model to quantum rotor model

For the Bose-Hubbard model: $$H=-t\sum_{\langle i,j \rangle}(b_i^{\dagger}b_j+b_j^{\dagger}b_i)+K\sum_{i}(\hat{n}-n_0)^2$$ In the large-filling limit, we can replace $\hat{n}$ by $\hat{n}+n_0$, and ...
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3answers
65 views

Regarding assumptions

In most of the theories or derivations we take some assumptions like has is ideal, frictionless piston and many more but these are not applicable in real world. But in our real life situations we ...
4
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0answers
67 views

Has anyone ever actually considered a spherical cow? [closed]

Yes, I'm aware this question is somewhat whimsical. I'm sure every physicist is familiar with "Consider a Spherical cow". Has a cow (or any animal for that matter) ever been assumed spherical for ...
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1answer
70 views

Vacuum Conditions in teaching high school physics

I'd like to know why in high school physics is taught mostly in vacuum conditions instead of terrestrial ones. I don't mean one is more important than the other, but it's just a curiosity about that.