Sign Definition and 579 Threads

I recently made a post on Linear and Abstract Algebra and used the following symbol $$ {\bigcup}_{\Omega \subseteq \Gamma , | \Omega | \lt \infty} $$ However, I really wanted (for neatness and clarity) to have the term $$ {\Omega \subseteq \Gamma , | \Omega | \lt \infty} $$ actually under the...

I have a question, according to rules for the sign of x and y-acceleration; when I should use the negative sign for gravity (g) in a problem, because it's confusing since I've seen that according to my textbook when an object is free falling g is negative (therefore acceleration is -9.8 ms^-2)...

Building a large sign. I've attached a drawing of what I'm doing. I need to make sure that 8-5/8 pipe is sufficient for sign. I live in Oklahoma and we get some nasty winds as well. Please help. Any suggestions greatly appreciated.

Homework Statement I am having a little trouble using mesh analysis. I'm trying to stick rigorously to the passive sign convention, as I'm told that this is sensible. Consider the circuit diagram attached, where I have added the mesh currents in orange. In red are the polarities for the...

Homework Statement To show that sin A + sin B = +2|sin ((A+B)/2)*cos((A-B)/2)| is easy. However, it is not clear how to remove the absolute value signs to give the valid identity sinA + sin B = 2(sin ((A+B)/2)*cos((A-B)/2)) without having to go through many cases. Homework Equations...

Homework Statement Find the points of inflection of y. (See picture for y). https://scontent-b-dfw.xx.fbcdn.net/hphotos-prn2/v/1385610_10200987969443169_488083853_n.jpg?oh=d014eb5324c27653f6f94d43a08957b2&oe=5277D415 Homework Equations Inflection points occur where the concavity of...

Hey all, I am just doing Kirchoffs rules right now. So we have a couple sign conventions we were taught. I just need to make sure my reasoning makes sense for the 3 and 4 rule. 1. When we travel through a source of emf from + --> - we get a - voltage. 2. When we travel through a source of...

Might seem a little silly, but I just can't seem to get my head around it. In math, when we write (a + b)^2 = a^2 + 2ab + b^2 or 2 = 1 + 1 , we mean the quantity on the left side of = and the quantity on the right side of = are the same. In physics, when we write F = ma or E = mc^2, what's on...

predict the sign for delta Ssys CH3CH2CH3(g) +5O2(g)---> 3CO2(g) + 4H2 Homework Statement predict the sign for delta Ssys CH3CH2CH3(g) +5O2(g)---> 3CO2(g) + 4H20(l) The same question for N205(g) --> NO2(g) + NO3(g) Homework Equations The Attempt at a Solution I said the...

This was something I noticed as I was trying to practice solving PDEs using the method of characteristics. The text has the following example: $$\frac{\partial u}{\partial x} + x \frac{\partial u}{\partial y} = 0$$ This should be easy enough. I let p(x,y) = x and solve for \frac{\partial...

Homework Statement This is a problem I made myself, I was curious to see if I'm understanding this convention properly. The link: http://gyazo.com/24c7f7f82f6453a3396d96d67c2a067d Homework Equations ##P=IV## The Attempt at a Solution Okay, from what I understand, the power...

I am sorry if I am doing anything wrong. I'm new to this site and physics in general. Please feel free to correct me if I'm making some stupid mistake in formatting. 1. The first figure gives spring force Fx versus position x for the spring–block arrangement of the second figure. The scale...

Homework Statement \sqrt{-3y-8} = -\sqrt{y+4}+2 I need to square both sides in order to solve for Y. But, how do I distribute the negative sign on the right side? Would it be similar to (-x+2)2 or -(x+2)2?

Energy of system of magnetic dipoles is ##E_H=-\mu_0 \vec{\mu}\cdot \vec{H}=-\mu_0\mu_zH## why sign ''-''? and ##\mu_z=-g_J\mu_Bm## Again why ''-'' sign ? ##z## is choosen to be quantization direction, and along that direction is applied field ##H##.

Sorry I'm not sure how you get math script on here, so have had to attach it. It is a differential under an integral sign and I'm not too sure how to approach it. Would you use Leibniz rule? Do you differentiate or integrate first? - where y is a function of x, and R of y Thanks in advance

Recently I had a fairly serious case of cubital Tunnel Syndrome with symptoms of hand clawing and Froment's sign. However I have been told Froment's sign never happens with cubital tunnel syndrome. However the book "Anatomic Basis of Neurologic Diagnosis" states that Froment's sign is a cardinal...

Hi; According to Wiki the minus sign is a unary operator (a negator). Calculations are done right even if the minus sign is considered to be a (-1) multiplier. How to explain, for instance, -(a+b)=-a+-b if the sign is considered an operator? Thanks...

Is it okay to perform operations under the limit sign just as we would if the limit sign were not there? I'm really asking this to better understand how to derive the value of e. e is defined so that its exponential function is its own derivative. I won't go through all of it (since I'm sure...

I was reading about Galileo's gravity and there I came across the formula. F= -mg. Galileo said that Force is proportional to mass but in the opposite direction. I don't want to discuss whether he was right or wrong. I just want to ask that when he replaced the proportionality sign and...

Here's a petition trying to get the USPS to run a stamp series honoring SF/Horror writers, editors and artists. It sure beats the hell out of another series of flowers...

Homework Statement Find Vad and VebHomework Equations voltage drop, KVLThe Attempt at a Solution I actually did: Vad -24V - 4V + 6V = -22V but this is wrong.I know going the other way Vad: 6V + 8V + 12V = 26V, because it is only drop, and plus to minus on drops means they are...

I'm having trouble determining the sign conventions for the appropriate moments and which forces correspond to the appropriate moment analysis in the following question .The solutions are provided but i still need to know the fundamentals behind such selection and the sign conventions for it as...

Hi all, I've been trying to figure out why this statement is true: \frac{r}{r+b} > \frac{r-1}{r+b-1} \quad \text{for all } b>0 I can't seem to reason it out. I've plugged in a few values greater than 0 and yes, it works out. But I don't understand how I can look at this and find it true...

With the Levi-Civita connection, the Killing's equation is: \xi_{a;b}+\xi_{b;a}=\xi_{a,b}+\xi_{b,a}-2{\Gamma^{c}}_{ab}\xi_{c}=0 I can't understand why there is a minus sign in front of the Christoffel symbols. We have that: \xi_{a;b}=\xi_{a,b}+{\Gamma^{c}}_{ab}\xi_{c}...

Homework Statement a 54.8 kg uniform square sign, 2.00 m on a side, is hung from a 3.00 m rod of negligible mass. A cable is attached to the end of the rod and to a point on the wall 4.00 m above the point where the rod is fixed to the wall. Homework Equations The Attempt at a...

Homework Statement The problem is here: It is question #4, http://faculty.mint.ua.edu/~pleclair/ph125/Exams/Ex3/ph125_s09_exam3.pdf Homework Equations See BelowThe Attempt at a Solution I have already gotten the answer and know it is correct: (2m*vi*d)/(((M,clay)+2m)*R^2) where m is the...

Hello A neutral charged object can be attracted to a charged body due to electrostatic induction.A charged body will induce charges of opposite polarity in the neutral body ,hence causing attraction. But is it possible that two bodies having same sign charges ,say two positive bodies...

1. Homework Statement Hi I was trying to see if I did this right. A shop owner wants to hang a sign of mass 200 kg which is supported by which is supported by a uniform 155 N beam. What is the tension in the guy wires and the horizontal and vertical forces that the wall applies to the beam...

Homework Statement Please help me confirm my answer. A shop owner wants to hang a sign of mass 200 kg which is supported by which is supported by a uniform 155 N beam. What is the tension in the guy wires and the horizontal and vertical forces that the wall applies to the beam? The length...

Let \gamma^{\rho} \in M_{4}(\mathbb{R}) be the Majorana representation of the Dirac algebra (in spacetime signature \eta_{00} = -1), and consider the Majorana Lagrangian \mathcal{L} = \mathrm{i} \theta^{\mathrm{T}} \gamma^{0} (\gamma^{\rho} \partial_{\rho} - m) \theta, where \theta is a...

Hello all, I am having some trouble calculating a convolution. For the question, and my attempt at a solution, please take a look at the pic. Can someone please point me in the right direction?

1. The sign Ye Olde Tavern is supported by a horizontal beam (A-C) and a cable (B-C). The sign has a weight of W= 294 N. a) Take (Summate) the torques of the system about point A then find the tension in the cable. b) Find the vertical force on the wall attachment at point A by taking torque...

On my DE test, I was asked to determine if two solutions to a DE are fundamental solutions. So I confirmed they were both solutions, and took the Wronskian, which was nonzero. I got points marked off, and he put a minus sign in front of my wronskian result. Isn't the sign of the...

Homework Statement Use the figure to evaluate the function that f(x)=sin(x) f(θ/2) Homework Equations n/a The Attempt at a Solution x2+y2=1 x= -2/7 (-2/7)2+y2=1 y=√(6)/7 sin(θ/2)= +/- √(1-cos(θ)/2) (the whole function is over 2 inside of the square root) =+/-...

Does anyone know if the sign convenmtion from the metric tensor is linked to the sign convention in the Dirac equation. i.e is it possible to have a dt^2 - dX^2-dY^2-dZ^2 metric, with a (-,+,+,+) convention for the Dirac equation?

The two wires shown in the figure below are separated by d = 8.0 cm and carry currents of I = 4.85 A in opposite directions. d = 8 cm = 0.08 m d = 8 cm = 0.08 m r = 0.08/2 = 0.04 m 2d = 21.6 cm I (up) = 4.80 A I (down) = 4.80 A (a) Find the magnitude and direction of the net magnetic field...

Hi guys! Let \left \{ B_{t} \right \}_{t\in \mathbb{R}} be a one - parameter family of compact subsets of \mathbb{R}^{3} with smooth (manifold) boundary (e.g. one - parameter family of closed balls). In my context, each B_{t} belongs to a different constant time slice of Minkowski space - time...

I had some trouble reconciling signs while attempting to teach electricity to my students here. The topic is electric potential, potential energy, electric force, electric field, and work. After much thought - several hours - I have finally come up with a presentation that solves the issues...

I've read about it before and now I'm trying to learn it myself from Woods 'Advanced Calculus' (as well as other resources like http://www.math.uconn.edu/~kconrad/blurbs/analysis/diffunderint.pdf) In the pdf, it says the method concerns integrals that depend on a parameter...now couldn't we...

Homework Statement General question, but specific question here: "What is the maximum acceleration a car can undergo if the coefficient of static friction between the tires and ground is 0.80? Homework Equations I used Newton's 2nd laws and solved The Attempt at a Solution I...

I googled for lens formula's proof on the internet and found one here http://www.tutorvista.com/content/physics/physics-ii/light-refraction/convex-lens-formula.php The problem is that during the course of derivation, it is assumed that image distance is -u following the sign convention...

Three blocks, each of mass 7.0 kg are on a frictionless table. A hand pushes on the left most box (A) such that the three boxes accelerate in the positive horizontal direction as shown at a rate of a = 1.1 m/s2. What is the net horizontal force on block B? =15.4 N What is the horizontal...

My textbook does a very poor job of explaining how to assign signs to power: http://www.mediafire.com/view/?e0xr8j41tokujx6 It goes on to explain passive sign convention but it never explains active sign convention. Also, shouldn't the sign for power depend on voltage and current since power is...

I believe that I have found a serious mistake in the wiki entry about Potential Energy. notice the -ve sign in the formula on the web page. According to the article, the definition of this term is : the gravitational potential at a location is equal to the work (energy transferred) per...

If a Feynman diagram only involves bosons, then can you multiply all external 4-momenta by negative one, and still get the same amplitude? Looking at the Feynman rules this seems true. If the diagram has a fermion (as real or virtual particle), then it seems this is no longer true. I just...

Homework Statement Dear all I have a question concerning the Coriolis acceleration expression. I learned it as Ac = -2ω x v, where ω is the vector which indicates the rotation axis direction of Earth and v the velocity of a body that I want to check the Coriolis effect on. My...

Dear all I have a question concerning the Coriolis acceleration expression. I learned it as Ac = -2ω x v, where ω is the vector which indicates the rotation axis direction of Earth and v the velocity of a body that I want to check the Coriolis effect on. My question: where the minus...

Homework Statement Question is in attachment Can someone explain to me what the infinity sign is I'm new to this topic. All I know is that as a satellite goes to a higher orbit that the velocity decreases.

Prove the Identity by Using a Sign Reversing Involution (See Attachment)

In this question, my answer to part (a) is correct, & leads into (b). With (b) my answer is also correct, except for the sign. Can anyone help me figure what I need to do? Many thanks. Homework Statement Q. 90^{\circ}<A<180^{\circ} such that...