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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Why is my simple RK4 failing to capture adequate spring deformation?

I am setting up a very simple physical model for two colliding particles modeled as elastic spring's obeying Hooke's law. I have set up a numerical model for the collision and while the end stages of ...
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1 vote
2 answers
164 views

What "kind of math" is used in the standard model?

From the perspective of set theory, there is a large space of possible functions between different spaces. But in practically applicable models, we predominantly see a small set of operators used, e.g....
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How do I model the RF propagation of an UWB transient pulsed signal in MATLAB

I've successfully plotted the signal strength coverage map for a generic narrow band (read single frequency) horn antenna using MATLAB's in-built functions design(), txsite() and coverage(). MATLAB ...
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3 votes
1 answer
75 views

Are there physics models that accurately handle the assumption of having solutions that achieve finite ending times?

Are there physics models that accurately handle the assumption of having solutions that achieve finite ending times? Intro Recently I learned on the answers and comments of this QUESTION that the ...
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1 vote
1 answer
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Limitations of spring and dashpot models in terms of strain meaningfulness

It is common to explain viscoelastic materials with spring and dashpot 1D constructions, e.g: which represents a Maxwell rheology, usually explained by saying that $ \sigma = \eta \dot{\epsilon}_1 = ...
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0 votes
1 answer
51 views

Is spacetime emergent?

Does space exist independently from its content, or is it in some way "created" by it? What I'm interested about is this question: Say we copied the standard model and duplicated its ...
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5 votes
1 answer
194 views

Shape of partly dissolved cube

Let's say you have a cube of some material, and you put it in a liquid that can dissolve that material. After a while you take out what is left of the cube. What shape will you have? I imagine it will ...
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2 answers
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How does massless particles arise in string theory when it starts with the assumption that all strings are composed of massive little pieces? [duplicate]

I saw in a lecture (see after 00:55:00) by Leonard Susskind, he write Polyakov action, saying that the string is supposed to have divided into several pieces with mass (he says that it is the non-...
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0 votes
1 answer
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What is the hydrodynamic limit exactly and why is it called that?

Hydrodynamics is one of those words which are used everywhere in the literature, but I can not seem to find a clear definition! My idea (which could be wrong) is it is a continuum limit of a theory ...
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0 votes
2 answers
42 views

Equation of motion of a particle in a sinusoidal well

Do you have solutions for the (classical or not) equations of motion of a particle in a sinusoidal well or just a quartic well, classicaly I would write the equations like so: $$\frac{d^2x}{dt^2}\...
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Interlink among different length scales of simulation and modelling techniques

I found this figure in the following paper A Review on Multiscale Modelling and Simulation for Polymer Nanocomposites However, I am skeptical about its correctness, as this paper is not peer-...
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0 answers
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Does physicists have a pre-conceived notion of continuity?

In many physics lecture on GR/ mathematical physics, one of the first things discussed is topology. I have seen many times that the reason for topology being discussed is that it's the weakest ...
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3 votes
2 answers
160 views

Why are winter jackets not commutative?

Say I have two jackets $A$ and $B$, which have some fixed parameters such as thermal insulation. Further assume each jacket can be worn on top of the other one without changing its parameters. Let $A\...
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How is the angle of the front wheel found in Bicycle Kinematics Model for a Car

My question is, in a 4 wheel model, the front wheels have different angles. To simplify things bicycle model is used. In the bicycle model, there is an imaginary wheel in the middle of the front ...
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30 votes
9 answers
4k views

Does amplitude really go to infinity in resonance?

I was recapping the forced oscillations, and something troubled me. The equation concerning forced oscillation is: $$ x=\frac{F_0}{m(\omega_0^2-\omega^2)}\cos(\omega t) $$ I don't understand why this ...
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0 answers
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Do most climate models use the absolute temperature or the temperature anomaly under the hood?

Climate models for the climate impact of anthropogenic global warming almost never report the climate impacts of the average global temperature reaching some absolute threshold. Instead, they almost ...
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Modeling an inverted pendulum but with motion of the cart stabilized by an external force

I would like to model an inverted pendulum on a cart with a little twist. For starters the cart has a motor that generates a force and applies it to the wheels. We can calculate the equations of ...
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1 vote
1 answer
52 views

When is classical electromagnetism applicable?

I'm currently studying intermediate level classical electromagnetism and I'm wondering, given that quantum mechanics is the suitable theory for describing the behaviors of microscopic systems, when is ...
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1 vote
0 answers
60 views

Opening a door to another dimension (Kaluza-Klein like model)

I start the subject with a small fantasy tale: You walk in a forest, until you find a door standing on the ground. You open the door, which let you enter a large room. You are surprised since that ...
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0 votes
1 answer
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Superposition of waves for changing frequency [closed]

Is this physically correct statement that the "superposition of waves increases with increasing frequency". An increase in frequency means smaller wavelength --> smaller path differences ...
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3 votes
1 answer
224 views

Modeling friction with Non-Lipschitz ODEs - Pendulum example

The main objective of this question is to figure out if the following differential equation have [finite-duration] solutions: $$ \ddot{\theta}+0.021\,\operatorname{sgn}(\dot{\theta})\sqrt{|\dot{\theta}...
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11 votes
6 answers
5k views

Understanding this quote by Feynman

This might be more of a question on semantics and interpretation and if this doesn't meet community guidelines, feel free to let me know and I'll delete it. It doesn't matter how beautiful your ...
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2 votes
3 answers
196 views

Logistic population equation and exponential model

In Verhulst's model of population growth and control, Let $K$ represent the carrying capacity for a particular organism in a given environment, and let $r$ be a real number that represents the growth ...
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0 answers
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Ways to think about hypothesis on cosmology and other physics fields

Context: Cosmology Lectures It is possible to write Friedmann's equation from Newtonian physics, e.g., following Leonard Susskind's lessons, having a grid that is defined in XYZ coordinates around an ...
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How to transform from a discrete to integral equation?

In this picture, the red curve is an elastic rod that has resistance to bending and extension. I am trying to model the adhesions (contact) between the rod and the substrate (glass): the green dashed ...
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2 votes
1 answer
64 views

Is it possible to alter any of Newton's three laws without altering the other two? If yes what will be the consequences?

Is it possible to alter any of the newton's laws without altering the other two? (We call such a system as a non-newtonian system)
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Modelling a Simple Linear Translational Mechanical System

I am trying to model the following translational mechanical system in I/O form, however I am unable to see how the force of the damper b12 is affected the force on M2. The damper b12 reduces the net ...
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0 answers
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If a photon is interacting with gravity why doesn't it posses gravitational field? [duplicate]

If a photon is interacting with gravity why doesn't it posses gravitational field? Fermions interact with electromagnetic field because they themselves posses electromagnetic field. All inert masses ...
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0 votes
1 answer
82 views

Quantifiers in physical theories vs reality

I understand a physical theory as a set of axioms/postulates like an axiomatic system in mathematics. When we use some theory to describe the physical world we assume that the axioms hold. In other ...
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5 votes
3 answers
379 views

Am I correct in saying "falsifiability is the feature of a scientific theory to be tested"?

Falsifiability is usually defined as "the extent to which a scientific theory can be proven wrong". Does this mean that falsifiability is basically the extent to which a scientific theory is ...
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9 votes
6 answers
3k views

How exactly do physicists reject and accept theories/models in physics?

I'm curious about the rejection/acceptance of a theory/model in physics. Is the only criterion to accept a model/theory is the explanation of data? Or are there more criterions? For example, we still ...
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0 votes
2 answers
90 views

Why was Rutherford wrong and Bohr was right (then)?

I read that Rutherford was ruled out because he predicted that electrons revolve around the nucleus and Bohr stated that accelerating electrons emit electromagnetic radiation and should collide with ...
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0 votes
0 answers
29 views

Model of a runner on a plane

I want to create a simulation of people walking/running on a flat surface. To this end, I need to have a kinematic model of their motion. It should be sufficiently simple, treating each person as a ...
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0 votes
1 answer
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Can postulates be proven wrong? [closed]

When Dalton gave his atomic theory, he postulated that atoms were the smallest indivisible part of matter. But now we know that they are composed of even smaller particles. So, the postulate has been ...
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-1 votes
1 answer
90 views

Proof for property of proportionality used in deriving physical laws like law of gravitation and coulombs law

$$\text{F} \propto m_1m_2$$ $$\text{F} \propto \frac{1}{r^2}$$ Therefore $$\text{F} \propto \frac{m_1m_2}{r^2}$$ In physics one quantity $\text{F}$ is directly proportional to two other quantities ($...
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2 votes
1 answer
51 views

Extreme oscillations and values in heat equation on a 1D closed ring

I am trying to create a (very) simple model of heat diffusion along a closed rod (e.g., a ring) with an initial condition in which one segment is hotter than the rest. I'm using the following formula: ...
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0 votes
2 answers
94 views

Simple Harmonic Motion: Equating Pendulum and Curved Track [closed]

This scenario is taken from the 2018 NZ Scholarship physics exam: (Just in case the image doesn't load, it involves a wagon on a curved track (concave up). The wagon moves down from one side, to the ...
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-3 votes
2 answers
66 views

Is it possible to make a magnetic box that will compensate Earth gravity allowing magnetic objects inside to fly on orbits like in space? [closed]

Is it possible to simulate solar system using magnetic spheres and some kind of box that will compensate the Earth gravity by magnetic force?
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1 vote
0 answers
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Mathematical prerequisites for M-theory [duplicate]

I am interested in learning M-theory; however I have no Idea as to what mathematics is required for it. Are the prerequisites the same as string theory? Is there more mathematical knowledge needed for ...
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1 vote
2 answers
135 views

Why is $\exp(-1)$ a good benchmark in many physics? [closed]

In many subjects in Physics (not only phys though), we often encounter a value which gives $\exp(-1)$, such as a time constant in circuitry ($\exp(-t/RC)$, $t=RC$ gives $exp(-1)$), lifetime, mean free ...
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0 answers
20 views

How to compute the Ocean tidal effect by giving the lat+long for specific location on a website?

I am quite new in this and interested in computation of contribution of the Ocean tidal gravity. I am following the website (http://massloading.net/ondemand_form.html) to get the data but I want to ...
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0 votes
0 answers
102 views

Stephen Wolfram Computational Model and the hypergraphs structure

I just discovered Stephen Wolfram`s project and model and I am fascinated especially since i had a similar ideea a few years ago without ever reading about it. I have a question regarding the ...
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21 votes
7 answers
4k views

Why are free parameters bad for a theory?

It is often said that one of the drawbacks of the standard model is that it has many free parameters. My question is two-fold: What exactly is a free parameter? My understanding is that the free ...
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3 votes
1 answer
153 views

Can artificial neural networks be effective theories?

Wikipedia describes "effective theories" as follows. In science, an effective theory is a scientific theory which proposes to describe a certain set of observations, but explicitly without ...
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-2 votes
3 answers
88 views

Could processes and outcomes which are happening in colliders be simulated via mathematical model?

Colliding particles either for the purpose of getting fresh yet unexplained experimental results or as a mean of testing proposed theories appears to be a very crude experimental method. Could area of ...
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0 votes
0 answers
26 views

Controling the temperature in test tube

I am an electrical engineer and I am trying to control the water temperature in the test tube (laboratory application). But I can't measure the water temperature directly. I know what is the heater ...
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3 votes
0 answers
57 views

Equation of motion for a coil around a mass, attached with a spring driven by magnetic field?

First of all, thanks for reading and hello! First time poster on Physics Stack Exchange. I'm an electronics engineer (so forgive my poor maths below!) and tend to hang out there. I have a questions ...
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0 votes
1 answer
42 views

Why are fluid properties continuous with respect to spatial variables?

I get the intuition behind the continuum hypothesis in which we may treat a fluid as a continuous distribution of matter if we’re studying the fluid at a macroscopic scale. But the continuum ...
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-1 votes
1 answer
73 views

How many quanta can travel at light speed relative to each other simultaneously? [duplicate]

How many quanta can travel at light speed relative to each other simultaneously? I know the concept of being "simultaneous" breaks down at a distance so let's assume for the sake of ...
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-1 votes
2 answers
99 views

Do all physical processes necessarily imply a computation is taking place? [closed]

I would like to understand if any and all physical processes taking place, necessarily imply computations are also taking place. As a motivating scenario for the question, consider the following: ...
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