Variables Definition and 1000 Threads

Homework Statement You wish to find the moment at the origin produced by a force, ̅F= {Fi}̂, that is applied at r= {̂ai+bj +ck ̂}. Which variables (F,a ,b,c , ) do we need to know to find a numerical answer? Explain using math and figures. Homework Equations Mo = r x F The Attempt at a...

consider an irreversible cycle. There will be no changes in the state variables (like U, S) of the system undergoing the cycle, but for the surroundings, there will be change in the state variables, in fact, entropy increases. my question is, what happens to the internal energy of the...

Why do we take a particle's position ##x## and its velocity ##\dot{x}## as independent variables in a phase space when they are dependent in the sense that given the function ##x(t)##, we can get the function ##\dot{x}(t)##? I'm thinking they are independent variables but not independent...

<< Mentor Note -- thread moved from the technical math forums >> I am getting stuck on this partial differential equation. Ut = Uxx - U + x ; 0<x<1 U(0,t) = 0 U(1,t) = 1 U(x,0) = 0 Here is my work so far : U = e-tw + x gives the new eq wt=wxx to get rid of boundary conditions : w=x+W Wt=Wxx...

I'm self-teaching through Tenenbaum & Pollard's "Ordinary Differential Equations", and for some reason I'm completely stuck on one of the problems, Ch.2, lesson 6, problem #6: Find a 1-parameter family of solutions for [...] the differential equation: 6) yx2dy-y3dx = 2x2dy. I didn't have...

I want to create an equation to make decision on the best product that i want to be the best for example: I have this 4 products: - product1: lives 1 months, quality 70%, people rating 50% - product2: lives 2 months, quality 60%, people rating 60% - product3: lives 3 months, quality 50%, people...

Hello all, Suppose I have the following summation ##X=\sum_{k=1}^KX_k## where the ##\{X_k\}## are independent and identically distributed random variables with CDF and PDF of ##F_{X_k}(x)## and ##f_{X_k}(x)##, respectively. How can I find the CDF of ##X##? Thanks in advance

Hallo, this is my first thread here. I have to do a double loop. I've a 1x4 cell containing 4 sources. For each of this sources i have a number of dataset labeled as source_pN where N is a number (a label for a group). I have to do a double "for" loop on sources and on each existing N to create...

Homework Statement Question: "If p and q are constants and x2+px+12 is equivalent to (x+3)(x+q), what is the value of p?" I was told that the answer was 7 but I am not sure how to reach this value myself. 2. Homework Equations I am not quite sure if this is applicable. The Attempt at a...

Let $a,\,b,\,c$ and $d$ be non-negative real numbers such that $a + b + c + d = 2$. Prove that $ab(a^2+ b^2 + c^2) + bc(b^2+ c^2+ d^2) + cd(c^2+ d^2+ a^2) + da(d^2+ a^2+ b^2) ≤ 2$.

I was doing this last week and now I'm drawing blanks on an equation with 2 variables. When you have a constant and a variable + a variable by itself, I forgot if I'm supposed to try to cancel the individual variable, or if I'm supposed to multiply/add it as a "like term". I'm not giving...

I get two different answers, ##a^2## and ##0.5a^2##, by using two different methods. Which is the correct answer? The family of curve for ##y^2=4u(u-x)## is given by the blue curves, and that for ##y^2=4v(v+x)## is given by the red curves. Method 1: Evaluate the integral ##I## directly in...

Hi all, This might be a simple question but I cannot seem to find any solution online I'm currently building a MatLab code for my project which involves in the ageing of certain artefacts and paintings, I've got most of it built but can't solve the simplest of problems of the start of the...

If there were nonlocal hidden variables that are indeterministic and doesn't obey counterfactual definiteness. What terms should they be called. I think hidden variable should only be reserved for deterministic counterfactual definite. What then should we refer to indeterministic...

Homework Statement Homework Equations Equation 1: 3x+2y+1/3z=50 Equation 2: x+y+z=100 The Attempt at a Solution I know that the variables go like this: x=5, y=2 and z=93. I solved this combining different variables until I got the right "combination". I have to prove these solutions, any...

Hi everyone I have a quick question about independent and dependent variables. Homework Statement The following data set gives the number of miles traveled, and the travel time in hours for each of the 10 car's driving assignments. Miles Time 90 9 40 5 90 9 90...

I have a model in which, for each store, predicted revenues are perturbed by a multiplicative shock: R = e^\eta r where r is predicted and R is observed. \eta is mean zero. I can find \eta as follows: \ln( r) - \ln( R) = \eta . I'm summing the squares of the \eta's. However, there are...

Hi. In most articles on Bell's inequalities, both the reality and locality assumptions are thrown at the reader from the beginning. DrChinese however starts with only the reality assumption and shows that it doesn't comply with QM IF it were possible to measure two non-commuting observables...

Homework Statement c & d are positive integers & 1/c = 1 + 1/d Now tell which is greater c or d? Homework Equations 1/c = 1 + 1/d The Attempt at a Solution 1/c = (d+1)/d c = d/ (d+1) c = 1 + d Thus if c =10 therefore d = 9 But this is not a correct answer. Some body please guide me. Zulfi.

Hi. I'm still confused about those three concepts. They sound pretty much the same to me, but this does not comply with Wikipedia's table of comparison of QM interpretations, where pretty much all combinations seem to be present. Actually, is the "Wavefunction real?" column even about...

Homework Statement evaluate ##\int \frac{sinh(ax)}{sinh(\pi x)}## where the integral runs from 0 to infinity Homework EquationsThe Attempt at a Solution consider ##\frac{sinh(az)}{sinh(\pi z)}## Poles are at ##z= n \pi i## So I'm considering the contour integral around the closed contour from...

It is often said that the Bell's theorem precludes local hidden variables. From a "modern" point of view one should never deduce conclusions from the existence of outputs in non commutative measurements. It seems that the derivations of this theorem use such results. Is there a proof which uses...

Homework Statement This problem actually has 2 parts. For vectors a= (2,p,8) and b= (q,4,12), determine the values of p and q so that the vectors are a)perpendicular b) collinear textbook answer: a) p= 1 and q= -50 (answers may vary) b) p= 8/3 and q=3 Homework Equations a*b = 0 a*b =...

Hello everyone, I have a theoretical calculus question. I am working on a exercise where you have to consider f(x,y,z) and express the variable z as a function of x and y on a certain level surface around a certain (x0,y0,z0). I found out that the condition for this to be able is that the...

Homework Statement Hi, If I have an equation in the form 0 = a*x^2 + b*y^2 + c*x*y + d*x + e*y + c Is it possible to solve this for y? Was hoping just to get a helpful link as this isn't for homework - just a personal project.

I am trying to work through a simplication of this factorial with variables: (n/2)!/[(n+2)/2]! I get, 2[n(n-1)]/2[(n+2)(n+1)n(n-1)] cancelling the 2[n(n-1)] leaves me with 1/[(n+2)(n+1)] However, Wolfram Alpha tells me this can be simplified as 2/(n+2) and I don't see that. Thanks

This question is driving me crazy. According to the textbook, the answer is 7/15, but I get 2/5. If anyone can tell me where I am going wrong I would be much obliged Here is the question Six fuses, of which two are defective and four are good, are to be tested one after another in random...

I was trying to do this exercise but my answer doesn't match with the solution and I'm wondering why: > Consider the variables transformation defined by $x=2u+v$ and $y=u^2-v$. Being $T$ the triangle with vertices $(0,0)$, $(1,0)$, $(0,2)$ on plan $uv$ determine the image of $T$ on plan $xy$...

Hi all, I have a nonlinear equation of the form: \frac{TP_x}{TP_R} = c_0 + c_1 U_R^n + c_2 \frac{T_R^2}{\sqrt{U_R}} This equation describes the relationship between tidal parameters and river discharge (velocity) in tidal rivers derived from the 1-D St. Venant equations. TPx is some tidal...

Homework Statement Given two two grounded concentric spherical shells with radii a,b (a<b) and a point charge q between them at a<r=R<b find: 1.The surface charge density of the point charge using the delta function, assume the charge is on the z axis 2.By using the separation of variables...

Hi, I have an optical model, fully programmably controllable with python. I want to know how much my variables (say N) of my model impact a certain parameter (i.e power, abberations). Now I have no clue how to go about this. There must be some analytical (numerical) method that I could use but...

If we have a function: \begin{equation} f(x,x',y,y',t) \end{equation} and we are trying to minimise this subject to a constraint of \begin{equation} g(x,x',y,y',t) \end{equation} Would we simply have a set of two euler lagrange equations for each dependent variable, here we have x and y...

Homework Statement Jeffrey is planning a large dinner party. His budget is $3000. He has the option of serving chicken at $30 per meal or roast beef at $40 per meal. The cost of the party can be modeled with the equation 30c + 40b = 3000, where c represents the number of chicken meals ordered...

Homework Statement Use the change of variables to evaluate the integral (x +y ) sin(x -y )dA, where R is the region enclosed by y = x, y = x - 2, y = -x and y = -x + 1. (Hint: use u = x + y and v = x - y Homework EquationsThe Attempt at a Solution Not sure how to start it

Mod note: moved from non-HW forum section Apparently doing math homework on Physics Forums helps me think more clearly. The d-part of this question gave me a headache, and I already wrote all of this LaTeX code on the homework side of this site, so I figured I'd post it even though I solved it...

Use change of variables to evaluate the following integral $$\int_{2}^{7}\frac{x}{\sqrt[3] {x^2 -2 }} \,dx\approx 8.577$$ $u={x}^{2}-2$ $du=2x\ dx$ $\frac{1}{2}du=x\ dx$ $u(2)=2$ $u(7)=47 $ $$\frac{1 }{2 }\int_{2 }^{47 }\frac{1 }{ \sqrt[3] {u }} \,du $$ Can't get same answer

In my electrical engineering Textbook, In the beginning of it, when they were introducing analog and digit signals, they said an analog signal was a signal that depends on some sort of changing continuous variable such as time. The later went on to say that Analog signals can be depending on...

Homework Statement The assignment is to find all values of k (in R) for which the system has 0 solutions, 1 solution and infinite solutions. If there are infinite solutions, find the amount of free variables. The system of linear equations: kx + (k+1)y + z = 0 kx + y + (k+1)z = 0 2kx + y + z =...

\begin{eqnarray*} &&\mathbb{E}\left( 1_{\left\{ X_{1}+X_{2}>\rho \right\} }X_{1}X_{2}\right) \\ &&\mathbb{E}\left( 1_{\left\{ X_{1}+X_{2}>\rho \right\} }X_{1}^{2}\right) \end{eqnarray*} where ##X_1## and ##X_2## are independent normal variables. I am wondering whether there exist closed-form...

Homework Statement I have problems with the following program which is long to post at once so I will explain what are the problems step by step. 2. The attempt at a solution 1. Define two structs that represents books and a bookstore as following: typedef struct { char id[14]; char...

When I was taking my introduction to C class, our professor heavily stressed that we were supposed to use local variables except when indicated otherwise. When we used C for microcontrollers with the same professor, he had the same requirement. Does this reflect a standard among computer...

By the definition of hidden variable (HVs); they are the parameters that determine what quantum states of two entangled particles will be after they are measured at particular measurement setups. Therefore and by definition, HVs should be reproducible and by undertaking measurements once or at...

Homework Statement At T1 the root mean square speed (rms) of compound P is 485.2 m s-1 and at T2 the rms speed is 504.1 m s-1. Using this data and the fact that T2 – T1 = 24.0 °C, determine the molar mass of P in g mol-1. Homework Equations From problem statement you have: (3·R·T1/M)1/2 =...

Homework Statement Solve ∇2T(x, y) = 0 with boundary conditions T(0, y) = T(L, y) = T0 T(x, L/2) = T(x, -L/2) = T0 + T1sin(πx/L) Homework EquationsThe Attempt at a Solution Set T(x, y) = X(x)Y(y) Then ∇2T(x,y) = (∂2X/∂x2) Y + (∂2Y/∂y2) X = 0 Rearrange to find two separate ODEs: d2X/dx2 =...

Let's say ##f(x)=ax^2##. Then ##d^2f/dx^2=2a##. Now we can make the change of variables ##y\equiv\sqrt ax## to give ##f(y)=y^2##. Then ##d^2f/dy^2=2##. It follows that ##\frac{d^2f}{dx^2}=a\frac{d^2f}{dy^2},## but I can't replicate this with the chain rule. I would put...

Loop variables: A line of force or flux that is closed to form a loop. Can a Photon be a line of force or flux that closes to form a loop?

Does anyone know of any books or online resources that do a good job discussing systems of linear 1st order PDEs with several (more than 2) independent variables? I am not a mathematician, but can handle graduate level classical physics with the associated applied math. Analytical and...

Hello, I am kind of new to Matlab so the questions I will ask probably sound a bit basic. Anyways, here goes: I want to create the matrix below which has both constants and variables. How can I do this? I know how to create a normal matrix (e.g. B = [1 0 2; 3 4 5; 0 2 3]) but I don't know how...

Hi. I have thought that the variables q and q' in L = L(q, q') are independent. (q' = dq/dt) Of course q and q' are functions of time t , but they are only dependent in terms of t . However, in the sight of general(or abstract? I mean, not specific) functional L(q, q'), q and q' are just...

I found this formula in a paper: \int exp( \frac{x1 + i x2}{ \sqrt 2} \eta^* - \frac{x1 - i x2}{ \sqrt 2} \eta) D(\eta)/ \pi d^2 \eta the author calls it the Fourier transform of D. It is the first time thar i see this formula. How common is this notation? Can we use it without problem?