2d Definition and 1000 Threads

Hey guys, I'm new to this forum and was hoping to get a clear answer regarding the difference between 1D, 2D and 3D flows in hydraulics (ex. 2D Numerical Model...) ? Thanks a bunch! -A.

Hello, Does anybody know/had experience with software that can turn 2D images to 3D models in CAD program, preferably in an offline environment (not on cloud)? The resulting model has to be accurate enough for aerospace engineering purposes. from looking online, I really didn't find...

Homework Statement A 42.5kg person is going down a hill sloped at 42.0 degrees. The coefficient of kinetic friction between the snow and skis is 0.180. How fast is the skier going 4.56 seconds after starting from rest? Homework Equations Is ffkmax equal to net force? The Attempt...

Homework Statement An object is hanging from three ropes. The first rope is vertical and has a tension of 16N. The second rope leads to the right and makes an angle of 70 degrees with the ceiling and also has a tension of 16N. The third rope leads to the left and makes an angle of 40 degrees...

Hi, I want to find out how thick/big/fat is the object in the image. For example, there is a tree in the image(photograph), I want to use MATLAB to calculate how big the tree trunk is. Problem: Find out the perimeter of trunk as shown in the first picture (named "perimeter.PNG". attached...

Homework Statement Si(001) has the following lattice vectors in a (2x1) reconstruction \vec{a'_1} = \vec{a_1} + \vec{a_2} \vec{a'_2} = -0.5 \vec{a_1} + 0.5 \vec{a_2} Calculate the reciprocal lattice vectors of the reconstructed unit cell, \vec{b'_1} and \vec{b'_2} in terms of...

So consider a 2D system with a circular potential and a spin-orbit interaction: V(r) = V_0 \theta(r_0 - r) + c r_0 V_0 L_z S_z \delta(r-r_0) where θ is step function. So the operators Lz and Sz commute with the Hamiltonian are are therefore conserved quantities. For the same reasons...

Homework Statement Consider a molecule with an electric dipole moment d. The Hamiltonian of a molecule in the external electric field E is: \hat{H} = \frac{\hat{L^2}}{2I} - dE \cos{\theta}, where the polar angle \theta characterises the orientation of the molecule. (We have chosen the field...

Homework Statement Let a and b denote two 2D vectors a = <a1, a2> b=<b1, b2> show directly that a . b ≤ ||a||||b|| Homework Equations The Attempt at a Solution Im looking for a place to start here. Should i start by computing the dot product of a and b and then also finding the magnitude of...

We have a region Ω in ℝ^2 with a smooth boundary. There is a plate of shape Ω and clamped edges which is approximated by the following equation: $$\frac{∂^2u}{∂t^2}=-Δ^2u$$ $$u(x,t)=0\hspace{4ex} x\in ∂Ω$$ $$Du(x,t)\cdot\hat{n}=0\hspace{4ex} x\in ∂Ω$$ \hat{n} is the outward pointing unit vector...

Homework Statement A stone is thrown horizontally from a height h above the ground (h > 0). The stone hits the ground after having traveled a horizontal distance x (x > 0). What is the expression for the initial speed v of the stone? Neglect air resistance. (please use the variables x and h...

1. Problem The kicker stands 50 m from the goalpost that is 3 m high. She kicks with an initial velocity of 24.5 m/s. She just makes the goal height-wise, but did the ball travel far enough? She kicked at an angle of 35.28 degrees. 2. Homework Equations S = (1/2)at^2 + V0t + S0 S =V0xt...

Homework Statement A block of ice starts from rest on an apartment building’s roof, which slopes at 41° below the horizontal. The block slides down the icy frictionless roof for 5.0 m and then leaves the edge, which is 12 m above the ground. a. How far from the building does the block strike...

Homework Statement http://imageshack.us/a/img812/8836/5tfn.jpg Uploaded with ImageShack.us Find F such that the moment around A will not exceed 1000N*m for any value of θ. Homework Equations M = fdThe Attempt at a Solution I got the right answer, I found the distance of a -> b AB= √( (2^2)...

Im sorry I just realized this is in the wrong subforum... Homework Statement Hello Everyone! I am new here and am having trouble with this webassign question. I was able to work out the answer to the first two but the last two are giving me trouble. I am not sure if this is right subforum to...

Hi! I am trying to compute the natural frequency of a system and I also need to add the added mass term to my equation. The object I have is a torus and is basically in heaving motion. I found a good paper, which gives a formula for 3d added mass and 2d added mass. I would figure that I...

Considering d=2 or d=3, the Ising model exhibits a second order phase transition at the critical temperature T_c, where the system goes from an ordered phase (spins preferably aligned in a certain direction) to a disordered one. This is reflected by the behaviour of the susceptibility, similar...

Hello, I hope this is the right section to post this question. While analysing the asymptotic value of a ratio of a bessel and a hankel function, I reduced it to something of the form [(1 + β/n)^ n * (1 + n/β)^ β] / 2^(n+β) ; n and β are integers and greater than 1 how do I show that...

Hi all, I would like to know if there exists any method to represent multidimensional vectors on a 2D plot so using extracting any unique features of those vectors. Can eigen values be used for such purposes like dimensional reduction. If so how ? I would like to know more about these...

I am a little confused about the Mermin-Wagner theorem, and the assumptions it makes, and I would like to better understand the 'exceptions' to the rule that occur in practical (non-ideal) scenarios. As is my understanding, The Mermin-Wagner theorem states that there cannot be spontaneous...

I think no matter what are the mass of two objects, there must be a fix angle between the angle of two direction. Is that using the center mass reference to calculate? I say that because we can prove that when the two objects with same mass collide, then the angle between the direction of the...

while it has been extensively proven that any 2D map can be colored with at most 4 colors, has any hypothesized why that is (outside the computer programmed brute force method)?

Hi. Me and my dad (math teacher) are having some trouble finding the answer to a seemingly fairly easy problem. It is somewhat similar to projectile trajectory math but with the difference that the projectile have an initial velocity and there's no gravity, only acceleration. Imagine the...

Homework Statement A ball rolling with an initial velocity of 40m/s[W] undergoes an acceleration of 5.0m/s2[N] for a period of 6.0 seconds. What is the displacement of the ball in the 6.0 seconds? The Attempt at a Solution Apparently the answer is 260m[W21°N] Please help!

Hi which 2D animation software would be good for adding simple animations in science class and for youtube presentations?. Eksamples would be: how galvanic cells work, simple biology drawings of cells, DNA etc. I’d like a program that’s quite straight forward but also gives me a lot of...

Hi, as I read in one of Hawking books, he predicted that a 2D life-form with an alimentary canal can not exist because it would fall apart. I was wondering about that, because I thought of an easy solution for this: with two movable chainings its still possible. I have made a graphic and...

Hi everyone, Is there a general method for finding out the moment of inertia of an irregular convex 2D polygon given the coordinates of its vertices? I have thought of one possible method: Split the polygon into multiple triangles and find the moment of inertia of each triangle around the...

Say I have a rectangle of width w and height h centred at (0, 0) on a 2D coordinate plane. The rectangle is free to move on a frictionless medium. It is not attached at any point. Case 1: A single force F = (Fx)i + (Fx)j acts at a point (x, y) How does the rectangle move? I looked it up on...

This is a problem that's appeared in a game I am writing, and is a bit beyond the mechanics I can sort-of remember from high school. The context is I have an object in 2D space which has a position p and a velocity u, and a goal position G I want that object to be in as soon as possible. At...

How to do integration for a 2D matrix using MATLAB? That is to say, suppose I have a bunch of data points over a rectangular region in xy plane, how to find the integral over this plane? More explicitly, suppose I want to integrate over a square region, [0,4]x[0,4] my data is 2 4 5...

Homework Statement So, I'm building a "Monkey Gun" and I want to be able to find the instantaneous velocity of my dart at a certain time. I shoot the gun at some angle, θ. The problem is, if I divide the velocity into x and y components, each depends on and impacts the other (the force from...

Homework Statement Consider metric ds2 = dx2 + x3 dy2 for 2D space. Calculate all non-zero christoffel symbols of metric. Homework Equations \Gammajik = \partialei / \partial xk \times ej The Attempt at a Solution Christoffel symbols, by definition, takes the partial of each...

A soccer player kicks a rock horizontally off a cliff 38.2m high into a pool of water. If the player hears the sound of the splash 3.13s later, what was the initial speed given to the rock? Assume the speed of sound in air to be 343m/s What I don't understand here is, determining the...

I'm looking for an analytical solution to a very simple problem I've come across. Start with a circle of radius a. Now place n points at random positions inside this circle. Can you calculate the expectation value for the mean distance between the points? For the sake of argument can you...

Homework Statement I am having trouble understanding how the following statement (taken from some old notes) is true: >For a 2 dimensional space such that ds^2=\frac{1}{u^2}(-du^2+dv^2) the timelike geodesics are given by u^2=v^2+av+b where a,b are constants. Homework Equations...

Homework Statement A person moving towards east with a speed 'v' observes the rain to be falling vertically downwards. When he doubles his speed, the rain appears to come at 30° angle with the vertical. Find the actual speed and direction of rain with vertical. Homework Equations...

Homework Statement I have a given Metric: ds^{2}=A(u,v)^{2}du^{2}+B(u,v)^{2}dv^{2} And I'm asked to compute its curvature, and use this result to compute the curvature of the poincare metric: Set A=B=\frac{1}{v^{2}} The Attempt at a Solution I'm using Cartan's method. So first I change to an...

Why is a single layer of atoms referred to as "2d"? I commonly hear a single layer of atoms referred to as being a "2-dimensional structure", when it so clearly is not 2-dimensional. Why do people make that obvious mistake? The same exact folks will also tell you that spacetime is a...

I've been trying to figure this out for long now but unfortunally, I'm not able to prove that ∇E = 0 in an Ohmic, 2d Hall conductor E = Rj + v×B with B = const (and orthogonal to j). There is quite a bit of subtlety involved in how to interpret v in that sort of ad-hoc generalization of Ohm's...

Hi I have this small doubt. i am not good in C . i like to bring i,j,pi values to subroutine and bring back Asi to main program. how to write ! Plz help.. #include <stdlib.h> #include <math.h> double A_operate(int i,int j) void main() { double Ai, pi[10][10],r[10][10]; int i,j,n,m; n=6...

Homework Statement A two-dimensional rectangular crystal has a unit cell with sides a 6.28Å and b 3.14Å. A beam of monochromatic neutrons of wavelength 5.0 Å is used to examine the crystal. Using either the Laue condition for diffraction or Bragg's Law, determine whether it would be...

Homework Statement In a game of billiards the 0.165 kg cue ball is hit toward the 0.155 kg eight ball which is stationary. The cue ball travels at a speed of 6.2 m/s and after impact rolls away at an angle of 40.0 degrees counterclockwise from its initial direction with a velocity of 3.7 m/s...

Hey everybody I've got a question for the programming savvy. I'm generating data which can generally be described by.. f(x,y) = Ʃn(an * xn)*Ʃn(bn * yn) Basically what I'm looking at is a data set which shows a surface which looks like about 1/4th of a wonky bowl. My trouble is...

When I was about 25 I noticed that a 2D photo appeared 3D when looked at through a magnifying glass. First I thought it depended on the lens, but then realized it was because I looked at the picture by just one eye - exactly as the camera lens had seen it in reality. I.e. there is much 3D...

Hello science folks! I've just started learning about trilateration. I am wondering if its possible to calculate the coordinates of a continuously growing circle(for example a sound wave) which hits three sensors at different times. I have added a picture so you can see what I mean. In the...

Hi, I'm trying to adapt the doppler shift formula for a stationary listener and a source traveling in a straight line towards/away from the listener to the case where the source does not move straight towards the listener. For example, suppose that I am looking north and train further in the...

Hello, for the Poisson problem Δu = -1 on a 2D circular disk with u = 0 on the boundary, we have average(u) = \frac{1}{8\pi}Area(disk), which is easy to see, as the solution is quadratic in the polar coordinate r. Does this (or a similar) relation hold for non-circular 2D domains? This...

Homework Statement A ball is kicked with initial velocity 40 m/s at an angle of 37 degree above the horizontal. What is the time (in seconds) needed to reach the maximum height? Homework Equations Y-axis h= Voy t - 0.5 g t^2 Vy= Voy - g t Vy^2= Voy^2 - 2 g h X-axis d= Vox t Vx=...

I'm currently working on a project for a code that does umbrella sampling of a 2-D Ising model [size LxL of a magnet (analyzing up or down spins)]. The next step is to take my code to analyze a nucleation region and its growth by varying the temperature above critical. Before I even attempt to...

Homework Statement We have this bridge, which is 2D - as shown picture. How I determine which sticks are subjected to pressure and which tension? How big are these forces? Sticks are intangible, mass of car is M. From the picture, we can determine the length of the sticks. Picture...