What is Sign: Definition and 592 Discussions

A sign is an object, quality, event, or entity whose presence or occurrence indicates the probable presence or occurrence of something else. A natural sign bears a causal relation to its object—for instance, thunder is a sign of storm, or medical symptoms a sign of disease. A conventional sign signifies by agreement, as a full stop signifies the end of a sentence; similarly the words and expressions of a language, as well as bodily gestures, can be regarded as signs, expressing particular meanings. The physical objects most commonly referred to as signs (notices, road signs, etc., collectively known as signage) generally inform or instruct using written text, symbols, pictures or a combination of these.
The philosophical study of signs and symbols is called semiotics; this includes the study of semiosis, which is the way in which signs (in the semiotic sense) operate.

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  1. torito_verdejo

    Electrostatics: sign of the potential

    The final result will only differ in its sign, but this is crucial. Having a positively, radially oriented electric field ##\textbf{E}##, I understand that the sign of the integral should be positive (## - (- A) = A##), but it is not! How and why is this the case? A line integral where the...
  2. A

    B Why the Sign Changes from < 0 to > 0 ?

    Why the sign change from < 0 to > 0?
  3. Like Tony Stark

    Doubts on the sign of acceleration

    What should I do? Because I have two possibilities. I have ##0=5+at## so ##-5/t =a##. But then I can also say that the acceleration is a negative because it is stopping, so I can write it like ##0=5-kt## and then ##5/t =k##
  4. F

    A G-parity - where does the minus sign come from?

    Hi all, I have a question on G-parity. I know it's defined as ## G = exp(-i\pi I_{y})C ##, with ##I_y## being the second component of the isospin and ##C## is the C-parity. In other words, the G-parity should be the C-parity followed by a 180° rotation around the second axis of the isospin...
  5. A

    I Clebsch-Gordan coefficients and their sign

    Summary: Different sign in the combination of two ##\textbf{1/2}## isospins with opposite third component Hello everybody! I was doing an exercise regarding isospin and I noticed something from the Clebsch-Gordan coefficients that made me think. For example, if I consider the combination...
  6. Simpcar

    Discharge in a DC RC circuit and negative sign of current

    Hi everyone! I'm trying to understand why when writing the differential equation of a discharging RC circuit V_C-Ri(t)=0 \to q(t)/C - Ri(t)=0 we replace i(t) with -\frac{dq(t)}{dt}. I read many threads but I don't understand the physics behind this. The usual answers I read are something like...
  7. Benjamin_harsh

    Explain why a negative sign is used before the 750(1.25)?

    ##R_{X} = \sum F_{X}## ##R_{X} = 750.sin 60^{0} + 250## ##R_{X} = 899.52 N## to the right. ##R_{y} = \sum F_{y}## ##R_{y} = 750.cos 60^{0} - 1250## ##R_{y} = - 875 N## ##R_{y} = 875 N ## downward ##R = \sqrt {R_{x}^{2} + R_{y}^{2}}## ##R = 1254.89 N## ## tan θ_{X} = \large \frac...
  8. Hawkingo

    Why there is a negative sign in the formula of calculating work done?

    $$W = - \int _ { a } ^ { b } \vec { F } \cdot d \vec { r }$$ ( The Force here is referring to the applied force, When moving a positive charge towards another positive charge(stationary) / field In this formula why there is a negative sign in the formula? I am not asking the sign of the total...
  9. Benjamin_harsh

    How negative sign appeared out of nowhere?

    I have to find resultant for this couples: My sir resolved given forces into components like this: He considered Fx couples for sides 3,4,5 triangles: He wrote resultant force for this above diagram: ##\Sigma F_x = \textbf{-}2*\frac{4F}{5}##
  10. J

    Simple clarification regarding the sign convention for work

    Precursor : Sign conventions regarding Work by the system/on the system may even vary among Physics textbooks and among Chemistry textbooks and as a rule of thumb it is better to clearly mark out the convention used by the text being referred to specifically and remain consistent with it...
  11. I

    How Do You Calculate Forces and Balance a Hanging Cafe Sign?

    A 3 kg cafe sign is to be hung from 1 kg horizontal beam such that it is in equilibrium. The beam is 4 m long. A wire is attached to the beam at its right end to prevent the sign and the beam from rotating. The beam is pressed against the wall on its left end and is prevented from sliding by a...
  12. S

    I Phonon Mass: Understanding its Sign and Effects on Gravity

    What is the sign of phonon mass? A substance of uniform composition, in a field of gravity, has pressure increasing downwards. This causes the compressibility to decrease downwards - and speed of sound to increase downwards. In a gradient of downwards increasing velocity, a wave propagating...
  13. Silverhobbiest

    I Significant Physical/Chemical Change Found by Sign Reversal?

    We know that "plastic" and "glass" charges were arbitrarily assigned to be negative and positive respectively, and electrons and protons were given their charges based upon that assignment (According to Randall D. Knight in Physics for Scientists and Engineers). I am curious if any significant...
  14. DaTario

    I Minus sign in Minkovsky´s metric

    Hi, Is there a simple explanation for the presence of a minus sign in the Minkovsky´s metric? Best wishes, DaTario
  15. WeiShan Ng

    [Fluid Mechanics] Negative sign on the viscous work term

    Homework Statement I am revising on the derivation of the differential equation of energy (White's Fluid Mechanics 7th ed) and I'm having trouble understanding the sign convention used in the viscous work term. The textbook first define an elemental control volume and list out the inlet...
  16. J

    B How do you create a + and π sign using multivariable (x,y,z)

    I am taking a high school multivariable calculus class and we have an end-of-semester project where we trace out some letters etc., except that they all have to be connected, continuous and differentiable everywhere. My group's chosen to do Euler's formula, but so far we are having problems...
  17. Zain580

    Why we don’t put a minus sign in Coulomb's law

    While calculating the force between two charges , why we don't put minus sign with charge.
  18. Mr Davis 97

    I Flipping the sign in the definition of derivative

    Is it true that if ##f## is differentiable at ##a## that ##f'(a) = \lim_{h\to a}\frac{f(a+h) - f(a)}{h} = \lim_{h\to a}\frac{f(a-h) - f(a)}{-h}##. That is, can the sign of ##h## be flipped. I've seen this a few times and it seems a bit dubious.
  19. E

    The sign of F (dot) dl when finding electric potential

    The electric potential can be defined as V = - ∫C E⋅dl where we are taking the line integral along C from some convenient reference point O, where we have set V = 0, to the point r we are trying to find the potential at. Of course, C can be any curve, but it's usually the most convenient to...
  20. Mr Davis 97

    I Showing that an infinite sum converges when a sign in the denominator is flipped

    ##\displaystyle \sum_{n=1}^\infty\frac{1}{n^2+n/2}## converges by the direct comparison test: ##\displaystyle \left|\frac{1}{n^2+n/2}\right| \le \left|\frac{1}{n^2}\right|##, and ##\displaystyle \sum_{n=1}^\infty\frac{1}{n^2} = \frac{\pi^2}{6}##. But what if we want to show that ##\displaystyle...
  21. beefbrisket

    I Sign mistake when computing integral with differential forms

    The question provides the vector field (xy, 2yz, 3zx) and asks me to confirm Stokes' theorem (the vector calc version) but I am trying to use the generalized differential forms version. So, I am trying to integrate \omega = xy\,dx + 2yz\,dy + 3zx\,dz along the following triangular boundary...
  22. S

    I Sign of the terms in a circuit

    Hello! I am a bit confused about the sign of the ##L\frac{dI}{dt}## term in the circuits (DC circuits). In my book it is defined with a minus, on wikipedia it is defined with a plus and I am not sure which one should I use. I can pick any sign I want and the result will come out right...
  23. Krushnaraj Pandya

    What is the Sign of Binding Energy for a Hydrogen-Like Atom?

    Homework Statement Is the binding energy for a hydrogen like atom equal to the total energy (negative) or the negative of the total energy (thus positive)? 2. The attempt at a solution I found varying answers and definitions, some places said binding energy's the energy required to disassemble...
  24. Krushnaraj Pandya

    Problem involving a derivative under the integral sign

    Homework Statement if ## f(x) ={\int_{\frac{\pi^2}{16}}^{x^2}} \frac {\cos x \cos \sqrt{z}}{1+\sin^2 \sqrt{z}} dz## then find ## f'(\pi)## 2. The given solution Differentiating both sides w.r.t x ##f'(x) = {-\sin x {\int_{\frac{\pi^2}{16}}^{x^2}} \frac{\cos \sqrt{z}}{1+\sin^2 \sqrt{z}} dz }+{...
  25. thariya

    I The sign of coupling Hamiltonian in CQED

    Hi all, I've always regarded the coupling Hamiltonian for a bosonic cavity mode coupled to a two-level fermionic gain medium chromophore to be of the form, $$H_{coupling}=\hbar g(\sigma_{10}+\sigma_{01})(b+b^{\dagger})$$, where ##b## and ##b^{\dagger}## and annihilation and creation operators...
  26. Mr Davis 97

    I Differentiating under the integral sign

    I am looking at a solution to an integral using differentiation under the integral sign. So let ##\displaystyle f(t) = \frac{\log (tx+1)}{x^2+1}##. Then, through calculation, ##\displaystyle f'(t) = \frac{\pi t + 2 \log (2) - 4 \log (t+1)}{4(1+t^2)}##. The solution immediately goes to say that...
  27. Greg Bernhardt

    Lingusitics Koko the sign language gorilla has died at 46

    What an amazing life and story! http://www.newsweek.com/koko-gorilla-sign-language-death-988302
  28. Mr Davis 97

    I SHM: Do We Need to Assume Sign of k?

    I have the equation for simple harmonic motion ##\displaystyle \frac{d^2x}{dx^2} + k^2 x = 0##. I have a simple question. Do we need to make an assumption about the sign of ##k## before we solve this? We have that the roots satisfy ##r^2=-k^2##. So ##r=\pm i \sqrt{k^2}##. Do I need to assume...
  29. A

    B What the equal sign means in physics

    For example F=ma means that the definition of force is m*a or the quantity of left side equals to the quantity of right side or both ? or kinetic energy..we know K=1/2mu^2 but is this the definition of kinetic energy or just the formula to calculate it ?
  30. E

    I Is the sign in this integral correct?

    In the table of integral, there is this formula \int_0^{\infty}\frac{sin(ax)}{x}\,dx=\frac{\pi}{2}\text{sign} a is sign a here is literally the sign of a, or it means something else?
  31. WeiShan Ng

    [Calc] Sign Convention in damping spring system

    Homework Statement A carriage is mounted on a spring, as shown in the diagram. The bottom of the spring is fixed to the ground. The carriage (loaded with its passenger) has a mass of 150kg. The carriage can only move vertically. The natural length of the spring is 10m and its spring...
  32. G

    Sign of the Faraday-Lenz equation

    Homework Statement Hello, good afternoon, I have a question that's coming up when I'm doing electromagnetic induction exercises. In some exercises they ask me to determine the electromotive force (iee), and when they do the exercise resolution they do it with absolute value. In other...
  33. EastWindBreaks

    What happened to the negative sign?

    Homework Statement Homework EquationsThe Attempt at a Solution I thought it would become d/dx(-kAc*dT/dx)+hp(T-T)=0 instead of where the equation in the red box? I don't see how are they equivalent [/B]
  34. MathematicalPhysicist

    I A minus sign in the gravitational potential

    So we have the Newtonian gravitation potential given by ##\phi_M(r)=-GM/r##, and in class the teacher said that the Newtonian force is given by ##F_m = -m\nabla \phi_M(r)##. Now, I was thinking about what was taught in UG or high school, isn't the force should be ##F_m = GmM/r^2##, if I plug...
  35. alijan kk

    Negative Sign of Binding Energy & Its Impact on Electron Energy in Bohr Orbits

    Energy of electron in nth Bohr orbit. En= -13.6 ev n2 what does this negative sign mean here ? and why the electron has less energy as we increase n ,, explain me with the help of electric fields and coulumbs law. :
  36. M

    How does the sign convention work in ray optics?

    Homework Statement I needed help to undestand some concepts in Ray Optics for my assignment. The topics which U am concerned are: Part 1: Mirror Equation, Refraction at singly curved surface, lens maker's equation, combination of thin lenses in contact. Part 2: Magnification Power of simple...
  37. Clara Chung

    I 2 sign questions related to the wave equation

    In the picture about, I gave 1. a picture of a segment of string for reference, 2. a description of the driving force and 3. a description about the potential energy per unit length of a point in the wave. I have two questions here. 1. Why does the driving mechanism produce a force to balance...
  38. A

    Sign issue with the skew bending formula

    Good day ! I have an issue with the sign minus inside the skew bending (unsymmetric) formula First we all know that the stress generated by the bending moment is the following: and then after we have the formula I really don't understand why we don t have the sign minus in all the formula...
  39. T

    Wilcoxon Sign Rank Test rejection region

    Homework Statement Two computer software packages are being considered for use in the inventory control department of a small manufacturing firm. The firm has selected 12 different computing task that are typical of the kinds of jobs. The results are shown in the table below. At the 0.05 level...
  40. T

    Distinguish between sign test and Wilcoxon signed rank test

    Homework Statement I know that for both method are used to test the 2 group sample for a non-normally distributed population ... But , i am not sure the difference between them . Can someone explain the difference between them ? When to use sign test and wilcoxon signed rank test ? Homework...
  41. T

    Sign Test Distribution Table

    Homework Statement In the photo above , H0 = the position of the plant doesn't affect the number of seeds in the pods . H1 = position of the plant affect the number of seeds in the pods The Attempt at a Solution This is a two -tailed test , am i right ? Referring to the normal distribution...
  42. nomadreid

    I Typographical question: the section sign

    I have seen the section sign \S mainly in legal documents. However, an acquaintance is writing a physics paper in which she uses this sign to refer to a section of another paper in which the section sign was not used (sections just being marked off by number), is it OK to use the section sign...
  43. T

    I QCD Sign Problem: Adding Quarks, Does it Change Properties?

    In ordinary mechanics, adding 1 particle to a system of 1000000 doesn't change a lot. I know about the sign problem in QCD, so when temperature is cold the amount of calculation diverges. My question is: when we add yet another quark to a system of 1000000 quarks, the amount of calculation...
  44. Anonymous123451234

    How Is the Vertical Force Calculated at the Hinge in a Beam and Sign System?

    A shop sign weighing 215 N hangs from the end of a uniform 155-N beam. Tension in supporting wire= 642 N Horizontal force exerted by the hinge= 526N Find the vertical force exerted by the hinge on the beam at the wall Fy= Fhy + Ft * sin() - mg - Mg =0 My attempt: Fhy= -(Ft *sin() - mg -...
  45. A

    Sign of a Function Homework: Find When Positive/Negative/Zero

    Homework Statement ##y = \sqrt {x+5} + \sqrt[3] {\frac {x} {4}}## Find when the function is positive/negative/zero. We were actually supposed to only calculate the domain in this exercise, but we had done some simpler and more basic positive/negative calculations before, and I was curious...
  46. N

    Does the Direction of Current Affect Ohm's Law Sign Convention?

    Here the voltage is negative so the current is negative. does it matter if I traverse the circuit through the other direction?
  47. S

    What is the Cartesian sign convention for microscope and telescope distances?

    Homework Statement Cartesian sign convetion for microscope,compound microscope and telescope. Homework Equations distances in the direction of incident ray are negative and thsoe along it are positive. all distances are measured from pole of lens or mirror. The Attempt at a Solution 1.FOR...
  48. P

    B Minkowski metric, scalar product, why the minus sign?

    In Schutz's A First Course in General Relativity (second edition, page 45, in the context of special relativity) he gives the scalar product of four basis vectors in a frame as follows: $$\vec{e}_{0}\cdot\vec{e}_{0}=-1,$$...
  49. F

    Sign convention of fixed end moment at cantilever beam

    Homework Statement I don't understand why the fixed end moment at AE is 10KNm ( clockwise) . Homework EquationsThe Attempt at a Solution Forger about the sign convention here , i have the resultant moment = 10KNm , which ic clockwise , why in the 2nd picture ( SFD and BMD part) , the moment...
  50. V

    How do you determine the sign of a magnetic field?

    Homework Statement Two long fixed parallel wires, A and B, are 10 cm apart in air and carry 40 A and 20 A, respectively, in opposite directions. Determine the resultant field (a) on a line midway between the wires and parallel to them and (b) on a line 8.0 cm from wire A and 18 cm from wire B...
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