Modeling Definition and 554 Threads

Hi there, so for my Differential equations class we are trying to model the vertical displacement of a curveball that is only in 2 dimensions, the X-Y plane, with Y being the vertical displacement, and X being the horizontal displacement. To do this we were told that the 2 forces acting on the...

As I've been reading up on fluid mechanics recently, I've discovered several different molecular models which attempt to explain heterogeneous fluid flow from a molecular level. Classical fluid mechanics assumes that hard body approximation- that atoms are hard spheres knocking into each other...

I'm trying to build a mathematical model of something like Heron's Aeolipile: http://en.wikipedia.org/wiki/Aeolipile I'd like to know, based on a known heat flux, the pressure and temperature attained in the container. I assume as water boils, the control volume loses mass and energy, the...

1. The problem dA/dt = -.02A dB/dt = .01A - .04B dC/dt = .01A + .04B A(0)=1000 B(0)=0 C(0)=0Come up with a sketch and a word problem involving three tanks for which the system of differential equations with initial conditions above applies. Have fresh water...

1. The problem Two very large tanks are each partially filled with 2000 gallons of brine. Initially 5000 ounces of salt is dissolved in tank A and 1000 ounces of salt is dissolved in tank B. The system is closed in that the well stirred liquid is only pumped between the two tanks. Four gallons...

I am trying to make sense of these articles http://info.kubotek3d.com/3D-Engineering-Software-Tools-Kubotek-Blog/?Tag=Direct%20CAD%20vs%20Parametric%20CAD and http://en.wikipedia.org/wiki/Explicit_modeling . To me this sounds like "if using parametric relations is too complex, let's stop using...

Hello! An assignment for my computational modeling course is to demonstrate the use of the Standard Euler method for modeling a simple harmonic oscillator; in this case, a mass attached to the end of a spring. I have the two coupled first-order differential equations satisfying hookes law...

I've formulated a method for modeling the flight of a rocket projectile. Can anyone read it over and point out any mistakes false assumptions, etc? thanks!

Hi, I need to find some good article or book related to the modeling of this process: the parcel of air goes up from the surface to the top of troposphere ( to 12000 m ), we know the conditions at the bottom such as temperature, pressure and humidity, we assume that the parcel is isolated...

The importance of modeling and simulation for understanding physics is a central question of didactics. System dynamics is a promising method to achieve this goal. This method is applied at the Zurich University for Applied Sciences (ZHAW...

I've been using MATLAB (ode45) to simulate the mechanics of a rocket under the forces of gravity, drag, and internal thrust.y I've recently refactored my simulation to include 2d space, orientation of the rocket, etc. (So I can try to make it orbit, finding optimal ascent profiles, etc)...

Homework Statement 1. The first part of the problem was to find a transfer function. Output is the displacement of the mass (mass of pinion is negligible) 2.The next thing to do was find the poles, which I believe means set the denominator=0 and solve for s. 3. The next thing to do was find...

Homework Statement I have a system of five coupled ODEs. I believe I should be able to reduce it down to four coupled ODEs, but I am not sure how. This system is modeling a quad X rotor where the arms are viewed as end loaded cantilever beams with motors attached. Homework EquationsThe...

I've noticed that the example of a particle in a box is heavily used even for physical situations where there is no obvious box: for example when finding the degeneracy pressure in a neutron star one calculates the fermi-energy from a 3D-particle in a box. So I wondered: is there any good...

Hello! I'm trying to model a car slowing down from speed with the forces of drag and friction and gravity from the road slope.. The model, which models the resistive forces is as follows.. [ Ffriction + Fdrag + Fslope ] / m = -a (deceleration) where: Friction force Ffriction = A...

Homework Statement Hello! I've been really unsure of whether my solutions to the first problem and part (b) of the second are right. My book gives few examples and so I've been trying to look on other websites for resources. Sorry if this is a lot, but any and all help would be appreciated...

Hello, I was hoping someone on here could suggest some affordable software to model the flow produced by a ducted fan. I saw someone using Solidworks flow simulation, which is convenient because I can use SW to model the fan AND get a rough estimate of the thrust produced. I'm not looking for...

Hi I'm currently modeling a 5-12Vdc buck converter, and just out of nowhere decided to put a transistor between the output resistance and the diode. Now, this transistor is always connected to voltage so it shouldn't do anything at all, it's just a closed switch. What happens is that the...

Hi, kind of stuck with how to calculate frictional forces in a particular problem: I am modeling yarn using mass spring system, zero dimensional nodes. Question is, what to do when a yarn can get stuck between a wedge? How to calculate friction force vector, surface reaction and so? Since a...

Help please with a problem from my modelling and optimization class. We're doing 2 variable optimization using Lagrange Multipliers. We're also discussing shadow prices. The first part of this problem is to maximize profit using the price and advertising budget assumptions and data. The data...

I'm interested in predicting the index of refraction of atmospheric air and several nonpolar gases at room temperature for pressures of 1 atm - 0 atm. I'm not really sure where to get started. I have found the relation n=\sqrt{1+\frac{3AP}{RT}} but I don't really get where it comes from. Well...

In my studies, I find myself coming back to the same question.How do we know all these things about matter. Its quantized, it has mass and, charge and blah blah blah. I understand that these models of the building blocks of "physical things" are well tested mathematical models that attempt to...

Hello all, I am calculating the loads on an unconstrained structure in space that is accelerating. There is a constant known force (T) being applied to it at one end (point A). The structure is a rocket with distributed mass but let's assume it is a uniform beam with constant density. I would...

ANSYS can be used to model creep in a number of different ways. If you are designing to ASME Section VIII, Div., 2 you might have to verify that your design meets the "shake down to elastic action" criteria. Basically, that means that the strains do not continue to increase over the number of...

Physics Forum: Can someone show me how to model, mathematically, what happens if you place a drink box with a straw sticking out of it, in a vacuum chamber and apply a vacuum?

Planck dust modeling has been released [re: http://arxiv.org/abs/1409.2495] . It appears to be consistent with the assumptions of BICEP2, but, that is an unsupported assumption. I expected an immediate reaction from the BICEP2 team, or other interested parties. Perhaps I am merely impatient, or...

Hello everyone, Assume that you have a flat plate, that is moving up and down in a sinusoidal motion with the following equation: y = yo*sin(2*pi*f*t) where yo is the amplitude of the motion, f is the frequency and t is time. There is another smaller size plate attached to the edge...

Hi, i am trying to model a triangle in a square cell based on its dimension. However, i have some problem with parts of the code, i think it might be the logic behind my programming or over definition with the code itself. i have attached the code. the problem lies with the second half of...

Hello PF, Can anyone recommend a set of governing equations for the design of a simple elastomeric balloon that will expand to a "hotdog" shape when inflated to a certain pressure? I have the stress-strain curve for the material, I know what pressure I need to inflate it to, I just can't...

Hello All, Firstly, I am very new to Scilabs/Xcos. I have some queries in modelling an asynchronous machine with a road load model. Can anybody save me ? Thank you in advance. Regards,

#1 Which of the following FUNCTIONS are SOLUTIONS (meaning PLURAL) of the differential equation $y''+y=sin(x)$? a. $y=sin(x)$ b. $y=cos(x)$ c. $y=\frac{1}{2}xsin(x)$ d. $y=\frac{-1}{2}xcos(x)$#2 Suppose you have just poured a cup of freshly brewed coffee with temperature $95^oC$ in a room where...

hello everyone is anybody here using comsol multiphysics? i'm trying to model a tube which the inlet is a fully developed fluid but the problem is how to enter a parabolic inlet profile for velocity in 2d axisymmetric it is very simple. but my model is 3d i've entered "r" as a variable in...

Hi, I am a beginner with the use of relap. So this might be a bit silly. I am studying the heat transfer between a fuel rod and a single channel of coolant. One of the inputs for the heat structure is the direct moderator heating multiplier. What is that and how do I find its value? Thanks...

I am starting a project on signal detection theory (cognitive focus), and working with a winbugs expansion in matlab. I am looking for good references, papers, books, anything that fully cover the theory of bayesian modeling and statistical inference (mostly with graphical modeling, since that...

I wanted to model a particular game and determine the probability for each team to win. I have no idea how to do the determination of probability part, but here's the game broken down: There are 3 types of players, T's, D's and I's. The amount of each type of player is as follows: 1/8 D...

This question is inspired by reading Arnold Neumaier's article on Everett's measurement theory: http://arnold-neumaier.at/physfaq/topics/everett Suppose I have a system whose state lies in a two-dimensional Hilbert space, and I want to model a measurement of its state as a unitary evolution...

OK, I'll dive in and start a climate change thread. I'm fascinated by the Nature paper by Abe-Ouchi, et.al., which I already uploaded in post #21 of this thread. If you look at Figure 1, the model does an outstanding job of modeling the last several ice ages. I have been somewhat skeptical of...

Dear all, I have a coupled system of ode's with an algebraic equation. The equations are as follows, function dy=lorentz(t,y) global Vfc; %fcdata.m % Data file for the hybrid system with parameters values %*************************************** % Physical parameters Rl = 0.024...

Hi there! My first post, exciting. What I'm after is a little help steering me in the right direction. I'm attempting to model evaporation in a closed system, and I'm not sure how to go about it. That is, let's assume we have a liquid in a partially filled container, and the rest is filled...

Why can't EM attraction/repulsion be modeled as spatial curvature the way gravity can be? And for that matter, why can't the strong and weak nuclear forces be modeled that way either? Or can they?

I can't model the potentiometer in speed governor control system by MATLAB even I know the input of it is pu and the output is voltage but when I run the program it has an error occur I want to see what wrong it is. Help me please

I am trying to model a shape T aperture through 2D rect functions. Both the horizontal and vertical 'lines' have length b and width a, and do not overlap. The origin should be taken to be the centre of the vertical line. The question has hinted at the function describing the aperture to be...

I would like to model rain hitting a surface and then running off of the surface. The surface would be a square, such as a slab of concrete, and the concrete would not be at any angle, so the rain would run off of all sides equally. This is a starting point for a small research project I am...

Two EE questions -- nodal analysis and circuit modeling Homework Statement Homework Equations I was given R1, R2, and Iα(t), the time for the switch to closed (50μs<=t<=100μs) The question is asking about the energy associated with 2 sources and dissipated in R1, R2.The Attempt at a...

Homework Statement I am trying to model using differential equations rain falling from the sky, hitting the pavement, and then running off the pavement into the ground. I'm a little rusty on differential equations and I'm just wondering if my answer is correct. In this model I'm assuming that...

I'm developing a scanner that uses a laser for edge detection. It will be mounted on a hexacopter that will traverse a short distance through a cave/tunnel system and produce a 3D image. I'm still researching on ways to process this data but I'm thinking of using a edge detection algorithm in...

Homework Statement Consider an item that is initially sold at a market price of $10 per unit. Over time, market forces push the price toward the equilibrium price, $20, at which supply balances demand. After 6 months, the price has increased to $15. the Evans Price Adjustment model says that...

Homework Statement Suppose water leaks out of a barrel at a rate proportional to the square root of the depth of the water. If the level starts at 36 in. and drops to 35 in. after 1 hour, how long will it take for all the water to leak out of the barrel? I have to choose and implement a...

First off, this is a typed paper project, and I am not asking for anyone to solve my work or to give me the answers. Just please point me in the right direction or help me through any parts I am not understanding. This is also a 7 part project, and I would like help on this first problem to get...

1. An object of unit mass is dropped from a height of 20 above a liquid-filled reservoir of depth 50. If the acceleration of gravity is 9.8 and the resistance-to-motion coefficients of air and liquid are 1 and 4, respectively, compute the time taken by the object to hit the bottom of the...