Sign Definition and 579 Threads

This is not actually a homework question but something I saw in a (economics) journal article and have been having trouble getting. It's very simple so I thought I'd post it here. Define the variable V (implicitly) by: V=b + \int^{rV}_{0} rV dF(s) + \int^{\infty}_{rV} s dF(s), where r...

Until today I learned in geometric optics that Object distance +ve for real object else -ve Image distance +ve for real image else -ve Radius of curvature +ve for if light comes to the surcace from the side lying center of curvature else -ve On the basis of this the lens formula...

Homework Statement A square coil of wire of side length 2a lies in the yz plane. A current I flows through the loop. The x-axis is defined such that it passes through the centre of the loop, with the loop boundaries being at z±a and y=±a respectively. Given that I flows in a direction...

Electric potential --- doubt in sign convention Homework Statement Revered members, I know dV = -E.dx so E = -dV/dx So E should be E = -V/x . But while deriving capacitance of a parallel plate capacitor when dielectric medium is introduced we use E = V/x. But how E = V/x? Homework...

A purple beam is hinged to a wall to hold up a blue sign. The beam has a mass of mb = 6.2 kg and the sign has a mass of ms = 15.1 kg. The length of the beam is L = 2.78 m. The sign is attached at the very end of the beam, but the horizontal wire holding up the beam is attached 2/3 of the way to...

When we derive the relations between image distance(v), object distance(u) ond focal length(f) for mirrors or lenses (1/v+1/u=1/f and 1/v-1/u=1/f respectively), using the concept of similar triangles and alternate exterior angles, in the last step we apply standard sign conventions to get the...

Homework Statement I am currently doing some Hooke's Law problems. While I do not have any trouble with any exercise in particular, I do have trouble with the sign in the equation. Let's say I have a vertical spring and I attached a hanging mass m to it. The string will then stretch a distance...

The problem statement is "each of the four uniform links has a mass m. determine the horizontal force P required to hold them in place in the vertical plane as shown." I attached the solution, but I don't get when a force causes a +/- virtual work.

If I disliked math as a kid, is that a sign that I am not naturally talented in it?? From grades K-12 I never liked math one bit. But now that I am college I find myself much more interested in it. However, I am regrettably a very competitive and pretentious person so I am worried that this new...

1) q(x_{1,}x_{2,}x_{3})= x_{1}^{2}+5x_{2}^{2}+26x_{3}^{2}+2x_{1}x_{2}+10x_{1}x_{3}+6x_{2}x_{3} V=\{x=(x1,x2,x3)\in R^{3}:q(x)=0\} check if V is a subspace of R^{3} and find the basis of V? how i tried: i diagonolized it the representative by rows and columns and i see that q is...

Homework Statement I am integrating sin(x)^3cos(x)^3, I know the technique (I hope) and I get the right equation at the end. But if I ask wolfram alpha what the integral of the equation is and enter 0 into wolfram's answer and also enter 0 into my answer, the answers come out different. If...

Hi All, I am confused about what is meant in the mathematical definition for the energy of a signal. Why is it the integral of the magnitude of the signal squared? ∫(|f(t)|^2) How do I deal with the absolute value sign? I do not have much experience with absolute value signs in...

Here is my question. For example if i am standing on top of the empire state building and i define that to be height=0 and i define the downward direction to be positive. if i drop a mass does its potential energy increase based on my definition of direction? My actual problem was an exam...

I have tablet phone samsung galaxy tab... when I check the signal strength, it shows -82 dbm... I thought it is produced by the Signal PA (Power Amplifier) on the PCB... According to what I know, the signal from the handphone is so weak to reach the nearest terrestrial station on the...

Fast question :I noticed that often the EFE are presented without the minus sign in the source term, (G=kT instead of G=-kT) does that have some reason behind or is it just plain sloppiness?

Homework Statement Calculate the Z-transform of the function x[n] = u[n]-u[-n-1].Homework Equations X(z) = ZT\{x[n]\} = \sum_{n=-\infty}^{\infty}x[n]z^{-n} ZT\{u[n]\} = \displaystyle\frac{1}{1-z^{-1}}, ROC: |z| > 1. ZT\{-u[-n-1]\} = \displaystyle\frac{1}{1-z^{-1}}, ROC: |z| < 1. ZT\{x[n]\} =...

Homework Statement I had a question in my physics class today that was relatively easy but what I was confused about was a misplaced negative sign. "An electron is rotating around a proton at a distance R. The mass of the electron is me and the charge is -e. Find the period." Homework...

Hello, I'm having some issues with plane waves propagating through a medium which is: - linear - spatially and temporally homogeneous - spatially non-dispersive - isotropic - temporally dispersive - passive I know that permittivity, permeability and the k-vector are complex in...

Hello all who read, I was reading along in the book Advanced Calculus by Frederick S. Woods today and came upon this technique. I played with it a little on some sample problems, but I still cannot figure out what it has any relation to. My questions I guess are that, (1) what...

what does this simplify to: (-33/2)2/3 I use the exponent rules to multiply the fractions to get (-31) which comes out to -3, but the answer key says the real answer is 3. Is there something important when doing fractional exponent that I'm missing out? Thanks in advance.

I saw this rather odd symbol of the the greater sign on top of the less sign in my lecture notes. I am wondering if there is a name for this symbol and if signifies 'equal to' as well?

Just when you thought it couldn't get any worse: From http://newsblog.projo.com/2011/08/cranston-neighbors-upset-by-si.html" This is very bizarre behavior to be sure... harassing and bullying taken to an extreme... Rhody... :eek:

Problem,the equal symbol "=" in math is overloaded , as is the word "is" in language. Is there a list of all the meanings of = in math and the word is. For instance "is" can mean equal to , or element of a set. Are there generally accepted alternatives to the "=" sign, so one can be more...

Homework Statement if lim f(n) = s , prove that lim (f(n))^{1/3} = s^{1/3}. How do you know that as n approaches infinity, f(n) and s have the same sign. n is just an index in this case and f is not a function but a sequence. The attempt at a solution so we know that |f(n) - s| < epsilon...

Hi all, I've been using Faraday's law to find the EMF in a coil of wire in a changing magnetic field. EMF = -N (change in mag flux/change in time) for N loops I'm finding that the EMF is always positive regardless of whether the change in flux is positive or negative. I'm wondering at...

relative minus sign?? Hi, I have one question for you... to compute the matrix element for the process u d -> u d I want to use full SM, but I have one problem I'll give you the maths. process with W: <ud|(\bar{Ψ}u Ψd)(\bar{Ψ}dΨu)|ud> process with γ: <ud|(\bar{Ψ}u Ψu)(\bar{Ψ}dΨd)|ud> Z and...

Might be a naive question. In many places, specially in the Hubbard model, people use a minus sign before the tight-binding hopping amplitude. What does the negative sign signify for? Any special intention? Thanks.

I have to prove that \left\langle lm | \vec{\hat{r}} \times \vec{\hat{p}} | lm\right \rangle = \left\langle lm | \vec{\hat{p}} \times \vec{\hat{r}} | lm \right \rangle, where | lm \rangle are eigenkets of angular momentum operator \hat{L}^2 And I can't figure out a way to do this...

Homework Statement solve for x: 5|7-3x|+2=4|7-3x|-1 Homework Equations The Attempt at a Solution 7-3x>0 -3x>-7 x<3/7 {x|x<3/7} quantity is positive {x|x>3/7} quantity is negative I have never solved an equation with more than one absolute value quantity in it and am not sure how to start...

We were having our maths class a weeks ago and while studying quadratic equations our teacher asked us if there was an difference between x^{1/2} and \sqrt{x}. Up until then I had always assumed them to be the same thing. However he said that there was a difference and said that he would tell...

Pfff. I don't even understand what "signing a house" over means. I thought that when our parents die, it would be sold and the proceeds distributed evenly. Or something like that. But he is quite a character. I think he sold me my car illegally, for starters. He's had trouble with the law, is on...

hello i just sign up to thses forum recommended by a friend to help with mu assignment. i posted a few questions to get help on but no replies. how do i get more replies and help thank you

Homework Statement http://img64.imageshack.us/img64/7782/circleb.jpg I'm supposed to find the slope equation of the tangent line to the circle at point A. A = (2, 7) The circle's formula is (x+1)2+(y+3)2 = 25 The center point of the circle is therefor (-1, 3) So the slope from the...

Hello all. I'm trying to figure out how to determine the correct sign of paths and surfaces defined for calculating quantities in electromagnetic problems. For example, say there's a wire in the shape of a rectangular prism along the z-axis with some current density, \vec{J} . Then the...

What does the symbol \underbrace{=}_{\wedge} mean? P.S. : The symbol beneath the equals sign is meant to be a triangle.

From what I understand: P=+iv (current enters through the positive polarity of the voltage, implying that the element is absorbing power) and P=-iv (current enters through the negative polarity of the voltage, implying that the element is releasing or supplying power) I remember reading that...

Homework Statement Hi guys! I'm having trouble with this Problem. A thin uniform rectangular sign hangs vertically above the door of a shop. The sign is hinged to a stationary horizontal rod along its top edge. The mass of the sign is 2.40kg and its vertical dimension is 50.0cm. The sign is...

So today I noticed something pretty weird on an exit sign above a door in my school, looking somewhat like this: http://www.examiner.com/images/blog/wysiwyg/image/exit_sign.jpg The effect is pretty difficult to describe by words, since I didnt expect to see anything like that on it. But it...

Okay I realize that stars emit at least some radiation outside the visual range but I have seen stars with positive BC when I thought that most values are negative due to the radiant flux over all wavelengths being greater than its flux over a certain wavelength. Is the sign of the BC the same...

Homework Statement Hi! I am trying to figure out how to create a small square after a proof of some theorem or definition (normally all mathematical proofs are finished by adding a small sguare at the end of it) how do I fix it? It is normally placed on the right side.. Oh I found it...

Homework Statement I am having some trouble with a question. Here it is: David is driving along at 25m/s when he sees a stop sign ahead. He hits the breaks at 10m from the sign. He decelerates at 4m/s-squared. Does he stop in time? Homework Equations We were given the equations of motion...

Homework Statement find the inverse of y=2x^2-8x x>=2 I am in calculus b but forgot some of the algebra so I am not sure how to treat the root Homework Equations The Attempt at a Solution I am skipping steps y=2(x-2)^2-8 (y+8)/2=(x-2)^2 I know that x >=2 so f(2) =-8 and...

Homework Statement A 500N sign is dropped off a building. % seconds later it strikes the ground. Calculate teh Max KE and the origional PE of the sign Homework Equations The Attempt at a Solution I know I need to find at least three of these varriables Vo = 0 Vf...

I am having a difficult time determining the sign of work in electrostatic problems. I'm attempting to reason out a general rule based on the given examples in my book and to relate it to work done by gravity--but I'm getting two contradictory observations. I don't know if maybe there are...

I have three question regarding the electronic wavefunction \Psi Ques 1 What does value of wavefunction of any orbital signify ? Is it just a mode of calculating other quantities like probability amplitude etc. or does it have a significance in itself ? Ques 2 What does the...

I picked an idea from a famous painting (La Prominade by Monet), then painted it myself with several additional details (I incrporated modern day elements, dresses, buildings, landscape, etc.). It is a very different version, but it definitively resembles "la prominade". I was told by a friend...

Hey guys, So the sign convention for power is really confusing me. According to my knowledge, if a positive current is entering the positive terminal of an element, the voltage drops across the element and power is hence absorbed. Why does the question solution change the sign of the current...

Homework Statement http://s861.photobucket.com/albums/ab174/alkaline262/?action=view&current=momentum.jpg why is it + w instead of -w, it seems like it sould be negative because the recoil velocity is in the negative x direction you have to admit that is a ms paint masterpiece :D...

What is the resoning or the motivation for the minus sign in the space-time interval?

The two standard conventions for the Minkowski metric are diag(1,-1,-1,-1) and diag(-1,1,1,1). The physics comes out the same either way, but I'm trying to make a list of the things that change depending on the convention you use. The Klein Gordon equation is one - with the "mostly plus"...