What is Sign: Definition and 593 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. R

    A force acts on a particle based on position, determine work. Sign question.

    I have a question about this problem in relation to the way the solution manual handles it. Homework Statement A force Fx acts on a particle of mass 1.5kg. The force is related to the position x of the particle by the formula Fx = Cx3, where C = .50. IF x is in maters and Fx is in...
  2. O

    Moments Problem Regarding Sign Convention?

    Homework Statement The handle of the hammer is subjected to the force of F = 20. Determine the moment of this force about the point A. http://s3.amazonaws.com/answer-board-image/3214a2db-1a55-4648-b582-5f36f0f34451.jpeg Homework Equations Principle of moments: Mo = FxY - FyX The...
  3. H

    Design Large Sign for Wind Loads

    Howdy - We're a small nonprofit that hosts a single annual event. For advertising this event we construct a large sign on a hilltop that's visible from the nearby highway. In years past this sign would last a few weeks before it would be destroyed by wind. Obviously our guess on how strong...
  4. X

    Solving Work Negative Sign Homework Questions

    Homework Statement See attachment Homework Equations The Attempt at a Solution Why is it -umg(50)? Why negative? Also I think this has something to do with conservative force and friction, and I'm very confused on this. Any help would be appreciated thanks.
  5. A

    Sign convention for work of a gas

    if a gas is expanding,what will be the sign of the work done by it?
  6. K

    [extremely easy question] the sign (+v or -ve) of potential energy

    since no one answer i edit it again.we got the forumla, v1-v0= the negative integral 0f E dot with dr from 0 to 1. So assume we are moving a positive point charge from infinity against the electric field emits by a positive source charge to location p. since E=f/q, and f dot dr = fdrcos180...
  7. B

    Calculate Distance for Bob to Stop at Stop Sign

    Homework Statement When Bob applies the brakes to his car, it slows uniformly from 20.0 m/s to 0.0 m/s in 4.0 s. How many meters before a stop sign must he apply his brakes in order to stop at the sign? 80 m 60 m 40 m 20 m Homework Equations d=(20+0)/2(4)...
  8. J

    Differentiation under the Integral Sign

    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...
  9. P

    Sign convention in geometric optics.

    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...
  10. E

    Biot-Savart law My proof includes a negative sign

    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...
  11. L

    Electric potential - doubt in sign convention

    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...
  12. I

    Solving Tension in Hanging Sign: 117 N or Wrong?

    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...
  13. H

    Why do we apply sign conventions to optics formulae?

    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...
  14. S

    Why is there confusion with the sign in Hooke's Law equations?

    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...
  15. D

    Virtual Work-very confused about the sign conventions

    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.
  16. N

    Signs I'm Not Talented in Math: My K-12 Experience

    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...
  17. N

    What is the basis of V for q(x)=0?

    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...
  18. P

    Incorrect Sign In Trigonometric Integral Problem

    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...
  19. C

    Understanding Energy of a Signal: Integral & Absolute Value Sign

    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...
  20. V

    Potential Energy question Confusion on the sign

    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...
  21. X

    Why there is minus sign in my tablet phone signal strength?

    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...
  22. TrickyDicky

    Why is the sign in Einstein's equation's RHS often presented differently?

    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?
  23. B

    ROC in Sign function Z-transform

    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]\} =...
  24. G

    Negative sign in coulomb's law/centripetal motion question

    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...
  25. E

    Plane waves: sign of Re(ε), Re(μ) in passive media, attenuation angle

    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...
  26. M

    Chem e undergrad: did I just sign up for another death sentence?

    I'm a third year planning to graduate 1 semester early. Last fall, I took 18.5 credit hours and worked 2 jobs (paper delivery and research assistant). I was pretty wasted by the end of the semester. Subsequently, I got depressed the following spring semester and had to drop down to a part time...
  27. 5

    Integration under the integral sign

    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...
  28. T

    Exponents with fractions and - sign

    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.
  29. S

    What is the odd inequality sign I saw in my lecture notes?

    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?
  30. rhody

    Cranston residents protest sign urging cancer patient to die

    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:
  31. Alain De Vos

    Overloaded equal sign = and the word is

    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...
  32. C

    Proving "f(n) & s Have Same Sign as n Approaches Infinity

    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...
  33. N

    Finding EMF - why we ignore the negative sign in Faraday's law

    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...
  34. D

    Relative Minus Sign for u d -> u d Process?

    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...
  35. H

    Negative sign in hopping amplitude

    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.
  36. L

    Angular momentum theory problem probably wrong sign

    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...
  37. L

    Sign of Lambda cosmology homework

    In question 4 of this paper, I am trying to find the sign of \Lambda Since we have the vacuum einstein eqns G_{\mu \nu}=-\Lambda g_{\mu \nu} we can just contract to get R-\frac{4}{2} R=-4\Lambda \Rightarrow \Lambda=\frac{R}{4} So \Lambda will have the same sign as R Now given the...
  38. ECHOSIDE

    Absolute value appears on both sides of equals sign

    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...
  39. M

    Difference between unit-fractional exponent and root sign

    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...
  40. N

    My brother wants my Mom to sign her house over to him.

    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...
  41. P

    How to use these forum sign up a few min ago

    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
  42. Femme_physics

    The opposite slope means the opposite fraction, or opposite sign?

    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...
  43. L

    Question about oscillating currents. (the sign of the phase constant)

    Homework Statement This is more of a conceptual problem I'm having with in a problem. I'm trying to find the phase constant of the equation for a capacitor that is charging at time zero. I'm having trouble with figuring out what sign the phase constant should have. Homework Equations...
  44. B

    What happens to differential equation if sign is flipped

    Homework Statement consider the differential equation: (x^2 -1)y''+(1/x)y'-by=0 what happens to the equation if the sign of x is flipped? what consequences does the behaviour of the equation when the sign is flipped have on the solutions of the equation? The Attempt at a Solution...
  45. J

    Sign Conventions for Paths and Surfaces for Electromagnetic Calculations

    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...
  46. S

    The symbol beneath the equals sign

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

    Understanding the Passive Sign Convention: Explaining P=+iv and P=-iv

    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...
  48. L

    Angular Momentum of a shop sign

    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...
  49. F

    What Causes the Strange Effect on this Exit Sign?

    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...
  50. P

    Sign convention of bolometric correction

    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...
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