Modeling Definition and 609 Threads

Homework Statement hi I am reading Guenther & Lee, "partial differential equations of mathematical physics and integral equations" on the first chapter second section i think, on "Small vibrations of an elastic string" they give this argument: 1. consider a string of x length L, the string is...

Homework Statement Derive an equation of the form y=ax^b to model the given data: (35, 0.01) (28, 0.03) (20, 0.1) (15, 0.3) (11, 1) (9,3) (6, 10) (4.5, 30) Homework Equations Well, I know the answer is y = (7790 +/- 1246)x^(-3.698+/-0.1036) because that's what LoggerPro spits out, but...

I would like to model in ansys a one-half of a ring with variable cross-section. What is the easiest way to define variable cross-section for elements in ansys? Do I have to define 5 (for example) different cross-section for each of 5 elements, if I create 5 beam element with different...

Homework Statement A slab is in a steady state with temperature T0 at x = 0, and T1 at x = 1. The thermal conductivity is given by K(x) = K0e\epsilonx where |\epsilon| << 1. The governing equation is given by, \frac{d}{dx}(K0e\epsilonx \frac{dT}{dx}) = 0 (1). Obtain an approximation...

Detailed modeling of a Pulley System, HELP! Hello people, Currently I have a project of a pulley system, and I have to model it with fair detailed equations. Actually this continues from another thread I started sometime ago, but I made a new thread because now I'm continuing with the...

Homework Statement Sorry about the title; I accidentally hit enter instead of 'Shift'. It should read Logistic Modeling -- help integrating/solving for P If P(0)=2, find P(90). Homework Equations dP/dt=1/900P(9-P) The Attempt at a Solution my solution looks like...

Homework Statement When certain viral particles enter the bdoy, the replicate to 160% every four hours and the immune system eliminates these particular viral particles at the rate of 50000 viral particles per hour. Find an equation modeling this viral growth. Homework Equations N/A...

Homework Statement When certain viral particles enter the body, they replicate to 160% every four hours and the immune system eliminates these particular viral particles at the rate of 50000 viral particles per hour. Find an equation modeling this viral growth. Homework Equations N/A...

Hi all, I am new to Physics Forums. Threads in the forum are excellent. As a Mechanical Engineer, It helps me to discuss about issues encountered in my work and also get to know about issues faced by others in their Engineering practice… To solidify my understanding, I would like to know...

i am working on the vehicle full suspension model. I am in modeling phase , i am electrical student and i am facing some difficulty in the dynamic results . When i am giving road disturbance to the vehicle the pessanger seat is getting more bounce and oscillations as compared to body to which...

Hi all, I'm doing some theory for my research, and I'm stuck! I'm trying to figure out why the absorption spectrum peaks at 420nm for silver nanoparticles. I know that this is expected for silver--I understand conceptually what's going on... but am trying to show it mathematically. I'm...

hi, I'm working on Tm3+ fiber laser rate equation modeling using Mathematica. The rate equations I'm using for the model are largely based on the work of Jackson and King ("Theoretical Modeling of Tm doped silica fiber lasers", 1999), albeit neglecting some factors so as to simply the model...

I want to calculate or model the vibration phenomena of tubes (specifically carbon tubes, gun barrels etc): such factors as time before coming to rest, vibration cycle(s), frequency etc that different designs of tubes exhibit when subjected to a force. One question in particular I would like to...

Homework Statement Hey Everyone, I am working on a physics project in which we need to look at a basic physics model. I have a couple of quick questions regarding conduction and heat generated through a resistor. So I basically have a wire acting as a resistor that I want to run current...

I'm making something I can rest a camera on, face down, that needs to hold it in the same position upon being taken out and put back in. The camera has a "streamline" type design so I've decided to use some sort of molding that will fit its contours. I am at a loss as far as knowing what...

The differential equation dS/dt = kS + D represents the rate of change of savings when S = savings balance, k = interest rate, and D = deposit. Ive figured out the solution for the differential equation to be, S = cekt - D/k If somebody invest 20,000 each year for the next 40 years with...

Homework Statement A tank contains 70 kg of salt and 2000 L of water. Pure water enters a tank at the rate 12 L/min. The solution is mixed and drains from the tank at the rate 6 L/min. Find the amount of salt in the tank after 2 hours. I'm failing to figure out how to manipulate the...

Hi, I am trying to find some texts (and/or journal articles) related to the mathematical modeling of transient dynamics. I am a civil engineer and figured physicists/applied mathematicians could tell me where to look. The systems I am looking at are finite dimensional and tend to equilibrate...

Hi, Well i have tried modeling a PZT actuator in d33 mode in abaqus and the model worked as desired. But, when i m trying to model a piezoelectric sensor in d33 mode the results are not as desired. Just to check the modeling procedure, i gave same properties of the actuator to the sensor. For...

Hello, this article caught my attention: "Physical Modelling of Quantum Economies" http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1304630 It intents to develop dynamic economic models based on physical systems. So for example: it introduces the concept of "price-space"; substitutes...

I will not comment about earthquakes and tsumani's. However, there has been an increase in extreme precipitation events due to global warming/greenhouse gases. Basically, greenhouse gases have increased the ability of the atmosphere to hold water vapor. It is not that there are more...

Hello all! I am looking for a method to calculate or model a resistance of a complex 3-D shape. For example if I have the resistivity of a material, and I know the shape (let's say a cone), I would like to be able to model the resistance which this shape will produce. I am looking for...

Hi, I have a data set where temperature and precipitation were monitored for a series of days at 5 ephemeral freshwater wetlands on various years (i.e. each wetlands was in a different spot (state even) and was monitored for a slightly different time period in anyone year/wetland). Over this...

Homework Statement Starting from rest, a 64.0 kg person bungee jumps from a tethered balloon 65.0 m above the ground. The bungee cord has negligible mass and unstretched length 25.8 m. One end is tied to the basket of the balloon and the other end to the person's body. The cord is modeled as a...

I want to model a toroidal transformer with a given permeability and saturation flux density. Specifically, I want to model a split core toroid clipped onto a power line, to simulate coupling, so it is really a one turn secondary and a primary of arbitrary turns. Any software packages out...

Homework Statement Assume that when the curve C shown below is revolved about the x-axis, it generates a surface of revolution with the property that all light rays L parallel to the x-axis striking the surface are reflected to a single point O (the origin). Use the fact that the angle of...

Hello all, Sorry for the long post. Skip to the line for the relevant part. As a longtime ultimate frisbee player, and also a computer programmer, I'm trying to write a program to simulate the flight of a frisbee for any given real-world conditions. I've read through the 5 or so papers I...

Greetings. I am trying to understand the common base amplifier better so I can build a preamp for a low impedance guitar pickup. In order to explore its operation, I tried to model it with the "approximated" Ebers-Moll model (from the wikipedia page on BJT's) and the graphing program in Mac OSX...

Hi all! I need to figure out a way I can predict the temperature range a small container of water (neglect properties small container and focussing on the water itself) will hold within an insulated expanded polystyrene (EPS) box of a given thickness, over a period of time. We can assume the...

Hi everybody! I am trying to model a lense shape using two circles of radii R and r, with one at the origin and the other offset upwards vertically by distance D. D must be less than R + r, but it must be greater than the larger of R or r. Thus, I have two equations, and the region of their...

Hi, Has anyone tried getting the voltage distribution of a biased solar cell with the poisson equation ( (d"V/dx") = (q/e)*(p-n) ) and electron and hole densities equation ( n = Nc*exp(-(Ec-qV-F)/kT) , p = Nv*(exp(Ev-qV-F)/kT) ) where Nc and Nv are the effective density of states, Ec and...

According to the following link a relationship lasts on average 3-5 years. http://www.answerbag.com/q_view/996515 If we take this as fact I'm curious what kind of mathematical model might be well, suited to describe this. The simplest model would be of the form: Let C - be the people in a...

A sky diver weighing 180 lb falls vertically downward from an altitude of 5000ft and opens the parachute after 10 s of free fall. assume that the force of air resistance is 0.75(v) when the parachute is closed and 12(v) when the parachute is open, where the velocity v is measured in ft/s. a)...

Hi, I have got a simple problem which makes me struggle. I have a rectangular thin conductive sheet (2D) of width w, height h and conductivity suspended in air. I would like to calculate with COMSOL/Femlab the electrical resistance between one of the corners of the conductive sheet and any...

Hi Everyone, I'm using Comsol v.3.4 to model a 1-meter copper rod experiencing a Temperature change of 294 Kelvin (4K at bottom and 300K at top). I have a slow computer/connection to the server, so I can't see any 3-D images or the Temperature plots. I'm working in the axial symmetry (2-D)...

Hello, In engineering, for instance, we set up the problem mathematically, and solve it mathematically. The question is: How did scientists interpret the physical systems into mathematical systems? and based on what? Did all come from experiments? Regards

I've noticed that plastic cups exhibit some interesting physical behavior. Some paper cups(maybe all actually, I'm not sure) have concave bottoms, and when the liquid in the cup gets high enough, the forces from simply raising the beverage from the table to my mouth create enough force to pop...

Homework Statement The amount of water in a storage tank, in gallons, is modeled by a continuous function on the time interval 0<=t<=7, where t is measured in hours. In this model, rates are give as: (i)The rate at which water enters the tank is f(t)=100t^2*sin(sqrt(t)) (ii) The rate at...

Homework Statement Im pretty much looking for a little push in the right to direction as to how to get me started on using a differential equation to model the up and down movement of a solid cube in water when a.) it is never submerged, and b.) when it can be completely submerged. The...

Hi For an initial approximate, I am modelling an aicraft wing as a cantilevered beam. I want to model the beam to incorporate the different materials used; a composite plate is sandwiched between a foam material and therefore the stiffnesses are different. How can I take this into account or...

I am thinking about ways to model physical systems. An example of the type of problem I want to look at would be the response of sound waves to a series of resonators. Here is a java applet of a ripple tank, which is along the lines of what I am thinking of. http://www.falstad.com/ripple/...

Hi everyone, I'm not sure if this is a basic EE problem as I'm in aerospace and I would like to apologize if i posted in the wrong forum. I've attached a circuit diagram of my design. The capacitors and the 2 higher resistors are of variable values. The switch and the lower resistor...

Hi, I want to model the em wave interaction to a metal ...can i do this without the RF module? I want to model the coupling of em waves to metal particles, so is it possilbe to do without RF module since my organisation have not subscribed for RF module... pls reply

o my bro ahd an algebra 2 midterm and a question was this: ) A printer costs $35,000 (how old are these questions lol) but it depreciates 5% a year. What is the value by the 4th year? ok so being an overtly complex person i tried to model a differential equation of this just for the kicks...

so my bro ahd an algebra 2 midterm and a question was this: ) A printer costs $35,000 (how old are these questions lol) but it depreciates 5% a year. What is the value by the 4th year? ok so being an overtly complex person i tried to model a differential equation of this just for the...

Homework Statement A hemispherical bowl 4 feet in diameter is full of a liquid. Show that the bowl empties through an orifice in the bottom, of one square inch effective cross section, in a little than five minutes. Homework Equations The Attempt at a Solution My problem is where to even...

Homework Statement Data suggests rate of growth of bacteria is proportional to the tangent function evaluated on the amount of bacteria present at time t, up to 1.5 mg. After 1.5 mg, value maintained. pi/6 to pi/3 mg growth in 1 hour. How would I write a DE equation based on this? I'm not...

I am trying to model a treybuchet arm. What I'm looking to achieve is an equation that shows the acceleration of the arm where the object is released. I have been looking into moments of inertia for the arm itself but I get stuck considering that there is a heavy weight used as Pot energy to...

Hi anyone explain me the Boussiensq's hypothesis( eddy viscosity hypothesis)

What are 10 big programs that are used today(in industry) for computation and modeling of physical sciences, specifically physics.