Model Definition and 1000 Threads

A model is an informative representation of an object, person or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin modulus, a measure.
Representational models can be broadly divided into the concrete (e.g. physical form) and the abstract (e.g. behavioural patterns, especially as expressed in mathematical form). Of particular importance in the modern context, conceptual models are central to philosophy of science, as almost every scientific theory effectively embeds some kind of model of the physical or human sphere.
In commerce, a model might instead reference a specific version or configuration of a product offering, rather than functioning as a representation of something else.
In taxonomic settings (e.g. biology, architecture, art) a model is sometimes a particular instance of a set of related entities (species, built structures, artistic compositions) chosen as a convenient reference point around which to build discourse; such a model is almost always chosen to typify some central tendency of the group, exemplify the group's defining characteristic, or reify the group's historical lineage.
Kinds of models include:

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  1. 2

    Differential gravitational force causing tides model?

    Homework Statement Homework EquationsThe Attempt at a Solution For a), I initially tried to consider the component of the gravitational force of the moon acting normally to the Earth's surface. This would be F=F_0 cos(theta) where theta is the angle between a horizontal line going through A...
  2. J

    Understanding the Bohr Model and Electron Decay

    Hi, I'm really struggling to comprehend how the Bohr model solves the problem of accelerating electrons losing energy and decaying into the nucleus. I've read through a lot of discussions on line and on PF and all I keep on reading is stuff like, the quantization of energy levels leads to a...
  3. P

    What is the three-body potential and how does it affect the baryon spectrum?

    Homework Statement I have to study the effect of the three body potential given below on the baryon spectrum. Homework Equations V(rij,rjk)=∑i≠j≠k≠i -V0(exp[-mrij]/mrij)(exp[-mrjk]/mrjk) where V0>0. The Attempt at a Solution Where can I find a discussion about this potential? I have no idea...
  4. C

    Question about the Limitations of Physics

    Here is a question about the possible limitations of physics, specifically about whether a theory of everything can actually explain everything. Assume we have a theory of everything. Now, consider an electron e with all the relevant properties. Now, our theory of everything, being mathematical...
  5. L

    Difference between Hubbard and tJ model

    What is the difference between Hubbard and tJ model? Does anyone knows?
  6. Abscissas

    Solving a Model Rocket Launch Problem

    Hello loves, I know there are post very very similar to this, but I just needed some help understanding it. any help is truly appreciated. 1. Homework Statement A model rocket is launched straight upward with an initial speed of 50 m/s. It accelerates with a constant upward acceleration of 30...
  7. E

    Material Model: initial conditions of equation?

    Hello guys, actually I'am working on a model to describe the creep-behaviour of a concrete specimen. This model is based on a 'generalized maxwell-chain'. I attached a picture, where you can see it: The acting load is the tension \sigma, while E_0 and E_1 are the stiffnesses of the...
  8. K

    Introduction to O(N) Model & Large N Expansion

    can anyone refer me to some good introduction to this O(N) model and also large N expansion. Thanks.
  9. E

    Model Rocket Help: Achieve a Glide for Contest

    I am trying to build a model rocket for a contest. It goes up as a rocket but comes down as a glider. Vertical takeoff. Does not jettison any parts. Should glide down in large slow graceful circles. Judged based on total hang time. I have been able to avoid a outright nose dive by putting the cp...
  10. B

    Question on the Standard Model

    I read in a magazine (namely Scientific American) that the Standard Model successfully combines Quantum Mechanics with General Relativity, but I also remember reading in The Elegant Universe that the Standard Model fails to do so. What's true and what's not?
  11. K

    MHB Positivity of compartments in epidemiological model

    Given the following dynamical model (system of ODEs): \begin{array} $ \frac{dA}{dt}=\Lambda-\mu A-\beta(C+D+E+F)\frac{A}{N}-\tau(B+D)\frac{A}{N} \\ \frac{dB}{dt}=\tau(B+D)\frac{A}{N}-\beta(C+D+E+F)\frac{B}{N}-(\mu+\mu_T)B, \\...
  12. 2

    Model of how temperature depends on latitude?

    Homework Statement I was asked to 'Use a very simple model to find how the Earth’s temperature should vary with latitude.' Homework EquationsThe Attempt at a Solution I was thinking about flux and how this should be proportional to the temperature. So I first thought about the area that is...
  13. E

    Why Electron & Neutrino Form Doublet in Electroweak Model

    Hello, I've unfortunately a trivial question, but one I couldn't answer by reading my references. In the Weinberg-Salam model, why do we take the left electron and neutrino spinors to form a doublet? I'd like a "physical" answer, if possible, and a more formal one, which I think is based on the...
  14. P

    Which gas model to use for dry air and N2 at 300 bar

    I want to calculate the change of state for N2 and dry air at pressures above 200 bar with a max of 300 bar. Ideal gas law is not applicable at these pressures, but looking at real gas models there are several to choose from, among others: Van der Waals Redlich-Kwong Virial Bender Can someone...
  15. N

    What is the full Lagrangian of SU(3)xSU(2)xU(1) model?

    What is the full Lagrangian of Standard Model?How can we build a Lagrangian that satisfies both the symmetry SU(3) and the symmetry SU(2) at the same time?
  16. T

    Solve Mass-Spring Model: Find Shear Force

    Homework Statement A half-full water tank mounted on the top of a building is modeled as shown below. Find the shear force it can produce? m = 500 kg k = 1000 N/m model: https://app.box.com/s/qke2kbwag2mp9a23kkqq Homework Equations Transfer Matrix Method: Point & Field Matrices...
  17. Ahmad Kishki

    What assumption leads to dB/dt=0 in the lumped element model?

    First assumption: the change of magnetic flux in time outside a conductor is zero. Last semester in circuit analysis we treated circuits with sinusoidal voltage variation as steady state circuits while using the phasor notation. But now that i know electrodynamics i begin to doubt my concepts...
  18. Hardik Batra

    How to 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 was why electrons don't emit EM waves & fall into the nucleus. I don't see how the introduction...
  19. M

    About COMSOL use to model Vanadium Redox Flow Battery (VRFB)

    Dear Friends, Merry Christmas to All. I am pleased to join this forum of Physics Experts. Please I need some help to work on COMSOL, I am about to start learning COMSOL. I'm going to work on this topic ' Vanadium Redox Flow Battery ' (VRFB) and this topic has many physics so it can be...
  20. E

    Is it possible to wrap a 2D texture onto a 3D model?

    In adobe photoshop, is it possible to take and wrap a 2D texture onto a 3D model? And is it also possible to make a 2D object from a photo into a 3D one?
  21. bhobba

    Is Physics Just a Mathematical Model?

    I participated in a recent thread where it was obvious the poster was confused about what physical theories are. Of course they are mathematical models, but they say the mathematics can't be the reality etc etc. I am sure regular posters here have seen the arguments - they appear with...
  22. marasciallo

    Frequency response function of periodic-stiffness model of system

    Hi, I'm analyzing a 3 dof undamped system with discrete springs and masses. Three of the springs have time-dependent stiffness, following periodic law (with period T), they are modulated at the same frequency but with a phase difference of 120 deg one from the other. So this is my system: (M *...
  23. A

    Model Fitting to Data - Scaling x Values & Shifting Parameters

    I have some (x,y) data with x in the range of 1e10 and 1e13, y is between 0 and 1. I am fitting this data using several theoretical models to gain an understanding of underlying mechanisms (by which model fits best). Using NonlinearModelFit in Mathematica, I get memory failures and cannot...
  24. fluidistic

    1-D Ising's model without B field, stat. mech., correlation

    Homework Statement Hi guys, I'm going nuts on a problem. Out of memory the problem was a system of N pairs of atoms that interact between each others so that the Hamiltonian of the whole systeme is ##H=-J \sum _{n=1}^N \sigma _i \tau _i## where the only possible values of the ##\tau _i##'s and...
  25. D

    Python Systems simulated by a simple percolation model using python

    I'm a first year physics student, and one of my assignment for my programming class is about percolation. I need to create some disks randomly distributed in an area (this is a 2-D), and then by varying the density of the disk, I need to figure out the percolation threshold such that the two...
  26. K

    What are the topological properties of the FLRW model?

    So, I was trying to do a derivation of my own for the FLRW metric, since I couldn't understand the one Wald had. The spatial slice M is a connected Riemannian manifold which is everywhere isotropic. That is, in every point p\in M and unit vectors in v_1,v_2\in T_p\left(M\right) there is an...
  27. N

    Please explain the Ising model in a simpler way, thank you

    Hello, can anyone please explain to me in a different approach, rather than repeating a book definition, what is the Ising model? and what conclusions were made from it? I would sincerely appreciate it, since I can't seem to grasp the concept even after reading numerous articles online and in...
  28. C

    How Do You Model Giraffe Population Growth on an Island?

    Homework Statement The growth of a giraffe population on an island follows a logistical growth model. The maxium giraffe population on the island is estimated at 1000. The population was first measured in 1970 at 125. Then in 1975 the population was 158 a) Find the rate of change in the...
  29. N

    Ising model, Hiblert space, Hamiltonian

    Can anyone please explain to me what is the Ising model, Hilbert space, and Hamiltonian ? However, please explain it as simple as possible because I am a freshman. I have looked up all three things. I've tried my best to make some sense of it, but I am, honestly, still confused on what any of...
  30. A

    Matching Reynolds Number in Scale Model Wind Tunnel Testing

    For my senior design project, I have to reduce the aerodynamic drag of a truck and trailer. I am doing CFD simulations and wind tunnel testing. The dimensions of the wind tunnel (test section) are 94 in long, 13.5 in tall and 20 in wide and a cross-sectional area of 270 in^2 and it could go up...
  31. Matt atkinson

    1D ising model - Helix-coil transistion

    Homework Statement A simple model of a polymer undergoing a helix-coil transition is to describe the polymer in terms of N equal length segments, each of which can be in either a coil or a helix state. A more realistic model also takes into account the energy cost associated with a boundary...
  32. P

    Is Mistletoe at PF TGI Friday's Our Role Model?

    Is that mistletoe that has appeared on PF? TGI Friday's is our role model?
  33. S

    Light Intensity Model: Showing Minimal Difference at Off Point

    Can someone assist with a simple model for the following question? I have looked on the net but cannot find anything on it. Say you are sat at a desk with the light bulb directly above you switched off and the rest on; so: on - on - on on - off - on on - on - on Each at distance r apart with...
  34. E

    How can I represent this circuit in state space?

    I have this circuit and I must represent it in state space. I know the process because I have done similar ones but having trouble with this one. I have found the Kirchhoff equtations for the 2 loops and for the upper juction, whatever I do after I can't end up to two equations x'1 and x'2...
  35. TrickyDicky

    The scale factor in flat FRW model

    In the FRW model with Euclidean 3-space, k=0 in the first Friedmann equation makes the density(times a constant) directly related to the Hubble parameter. The Hubble parameter is the time derivative of the scale factor divided by the scale factor itself. My question is: does a Euclidean...
  36. C

    Solving Antiferromagnetic Ising Model on Square Lattice

    Hello, I am trying to work out a mean field theory for an antiferromagnetic Ising model on a square lattice. The Hamiltonian is: ## H = + J \sum_{<i,j>} s_{i} s_{j} - B \sum_{i} s_{i} ## ## J > 0 ## I'm running into issues trying to use ## <s_{i}> = m ## together with the self-consistency...
  37. T

    Generalising the Ising model to multiple spin values

    My tutor asked us today to consider the partition function of the following model as an aside to our topic at the moment. I went to work out the maths of it today and I'm quite stuck for how the calculation can proceed. It's a 1d closed chain with some number, n, points. Each point has some...
  38. W

    Tight Binding Model: mathematics

    From the textbook of Omar: Can someone explain me the summation of this? I simply don't get it? Thanks in advance.
  39. mss90

    Energy transition (bohrs model)

    Homework Statement By using the Bohr model of the atom: whats the lowest energy transition from the n=2 to n=1 state in Hydrogen (Z=1) Homework Equations En = -13.6eV*Z2/n2 The Attempt at a Solution En = -13.6eV*Z2/n2 n=2 -> n=1 for hydrogen (Z=1) E2= -13.6eV*12/22 =-3.4 eV E1= -13.6eV*12/12...
  40. Vigardo

    How to export an ANSYS model into STL format for 3D printing

    Hi experts! Do you know how to export an ANSYS model into STL format? I´ve only found some method for solid meshes here http://www.padtinc.com/blog/the-focus/color-3d-printing-ansys-ansys-mechanical-and-mechanical-apdl-results, but my model contains only BEAM4 elements. Would it be possible...
  41. J

    Standard model, mass prediction

    Hi, I've read on the cern website that the standard model does not predict that matter inherently has mass, if this is the case how does the model predict particle masses and also why doesn't it predict that matter inherently has mass? Thanks.
  42. Z

    Transfer function of the state space model

    I have a state space model along with an observer and state feedback. I need to find the transfer function connecting the r (reference) to the y (output) I have this model on simulink. I know the A,B,C,D matrices. So, I can get the TF for the stateSpace with ss2tf function of matlab...
  43. P

    Exploring Bohr's Model: Energy Levels & Frequency of Transitions

    Homework Statement In Bohr's model the allowed paths are those which the angular momentum is quantized by L=ħn and the electromagnetic radiation emission is only by transition through two of them ν=(Ei-Ef)/h. I am asked to use the above assumptions to calculate the energy levels and the...
  44. F

    How Do I Find Constants for the JC Flow Stress Model in Waspaloy?

    Hi my name is Federico and I'm a student of mechanical engineering and i have to make a research on this material: waspaloy. Now, i have the flow stress model, but i don't have some constant of this equation. In particular , there are a classic JC model where stress is...
  45. S

    Quantum Dots and the "Particle in a 1-D Box" Model

    Homework Statement The "particle in a box" is the simplest quantum system. Despite this, it still reveals a lot of important new quantum features. Please use the "particle in a 1-D box" model to explain the reason why when the size of a quantum dot gets smaller, the wavelength of the emitted...
  46. T

    Trying to model the acceleration of a system due to an impulse forcing function

    Homework Statement My team and I are working on a design project to design/modify a device that can go on hikes for paraplegic/quadriplegic people. Here is the current design (not designed by us): http://i.imgur.com/RAOq28k.png http://i.imgur.com/zgA3aCg.png We are thinking of adding a...
  47. C

    Creating a Numerical Model for a falling Ball

    Homework Statement A ball was dropped through a known vertical distance with the time of drop also recorded. The aim of the task is to create a numerical model in excel in order to approximate the drag coefficient. Homework Equations This is my method. 1. FBD for the ball falling. (assume...
  48. E

    How to phrase a hypothesis for simulated model on a experiment report?

    Homework Statement I'm setting up an experiment for a simulation. I'm not sure how to formulate the hypothesis. The model used in the simulation is the first iteration, so I'm just using 2 attributes, 1 independent (A) and 1 dependent (B). As a result, I need to state explicitly that this model...
  49. M

    Replicating a 747-400 Wing Model

    Hello, This is in reference to a senior design project I must do. I have to create a 747-400 wing model in PTC Parametric Creo 2.0. The problem is that other than the wingspan, wing area, and sweep angle, Boeing does not reveal other crucial information such as taper ratio in order to find the...
  50. gonadas91

    Interacting resonant level model

    Hey guys this is my first question, I am trying to solve a first approach of the interacting resonant level model (IRLM), where we suppose that there is only one energy level acting as a quantum dot between the leads. The hamiltonian is of the form \begin{eqnarray} H=\sum_{kL}\epsilon_{kL}...
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