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. U

    Driver sees stop sign up ahead

    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...
  2. M

    How to know which sign of root to take when finding the inverse of a function

    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...
  3. J

    How Do You Calculate the Maximum Kinetic Energy of a Dropped Sign?

    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...
  4. C

    Determining the sign of Work in Electric Problems

    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...
  5. V

    Significance of wave function and its sign

    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...
  6. K

    Should I sign my version of a painting or not?

    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...
  7. M

    Power Sign Convention: Confused? Get Help Here!

    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...
  8. V

    Simple wuestion about the sign(+/-) in a momentum conservation problem

    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...
  9. K

    Why Does the Minus Sign Matter in Space-Time Interval?

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

    Metric Sign Convention: Effects on Klein Gordon & Dirac Equations

    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"...
  11. Telemachus

    Partial derivatives for the sign function

    Homework Statement Hi there. Well, I've got some doubts on the partial derivatives for the next function: f(x,y)=sg\{(y-x^2)(y-2x^2)\} Where sg is the sign function. So, what I got is: f(x,y)=f(x)=\begin{Bmatrix}{ 1}&\mbox{ if }& (y-x^2)(y-2x^2)>0\\0 & \mbox{if}& (y-x^2)(y-2x^2)=0\\-1 &...
  12. T

    Using divide as a 'sign' for a number

    A negative number has the minus sign as its own intrinsic operator. Has anyone thought of using the divide symbol in a similar way, and has there been any attempt to standardize this throughout math? For example (assuming / is the divide symbol): /5 = reciprocal of 5 = 1/5 = 0.2. It saves...
  13. T

    Sign of acceleration in the pulley-type question

    Homework Statement suppose an object A is placed on a horizontal frictionless table, and connected with a light inextensible string with a light, fixed pulley at the edge, and object B is only pulled by the vertical string that connected to a pulley. I tried to set the acceleration up and...
  14. M

    Sign Analysis of irrational functions

    Hi, I am from Belgium so i apologize for my English, I have encountered a problem, i don't understand how to set up the sign analysis of irrational functions, so i decided to find some information on the internet, but the problem is that I am not sure if "sign analysis of irrational functions"...
  15. D

    Why is the Inducted Voltage Negative in Book B's Dot Convention?

    Hello, I have a doubt regarding dot convention in magnetically coupled circuits. In book A, the following is stated: But in book B, this is stated: In book B, why the inducted voltage of the second mesh (-j w M I1) has that negative sign ? According to dot convention, it is supposed that...
  16. S

    Naive sign function for real numbers - challenge

    How would you solve this without using decisional blocks?
  17. n.karthick

    LaTeX Latex: Get Straight Integral Sign

    I am using Latex for typesetting technical document. The default \int command produces the integral sign in somewhat slanting style. But I need the integral sign which look straight as I get in Mathtype software. Even though one may feel, why can't I just accept the default style of integral...
  18. N

    Why does a diode have a specific sign?

    why diode has such a sign?? by the bottom sketch we have the diode to be short circuit but if we look at the upper sketch we see that the current (ie electrons) flows from the plus p side for diode to be short circuit we ned to have the electrons flow to the n side not to the p side...
  19. H

    Recursive function, diff under the integral sign

    Hey i stumbled over a problem which i can't solve: f is a continuous function on [a,b] and F_n is recursive given through: F_1(x)=\int_a^x f(t) \ dt and F_{n+1}=\int_a^x F_n(t) \ dt I have to proof that F_n looks like this: F_n(x)=\frac{1}{(n-1)!}\int_a^x (x-t)^{n-1} f(t) \ dt...
  20. T

    How Much Weight Can the Sign Hold Without Breaking the Cable?

    Homework Statement A 120-cm-wide sign hangs from a 5.4 kg, 200-cm-long pole. A cable of negligible mass supports the end of the rod as shown in the figure. What is the maximum mass of the sign if the maximum tension in the cable without breaking is 380 N?Homework Equations \Sigma \tau = 0The...
  21. K

    Does the Sign of the wt Term in EM Wave Propagation Matter?

    We were taught in the vibrations and waves lecture course that the solution to the wave equation for traveling waves is of the form ψ(z,t) = Acos(wt-kz). In the Electromagnestism course we learned that EM waves are traveling waves and have the solution E = E0cos(kz-wt). I know that changing...
  22. W

    What is the Torque Produced by a Beam and Sign on a Wall?

    Homework Statement a uniform 2kg horizontal beam is 50cm long is bolted to a wall and supports a 5kg sign. calculate the tourqe produced by the combined weight of the beam and the sign about where it is mounted to the wall. Homework Equations tourqe = F x Perpendicular distance The...
  23. B

    Sign of the following function

    0\leq x,y\leq1, \,\,a>0,\,\, \phi_{a}(x,y)=\frac{1}{a}\,x^{(1-a)/a}+\frac{1}{a}\,y^{(1-a)/a}-\frac{1}{a^2}\,(x\,y)^{(1-a)/a} . In which case depending on the value of the parameter "a" ,the function \phi_{a}(x,y) \geq 0 . Thanks
  24. Aquafire

    NASA Help NASA return to the Moon : Sign the Petition.

    As most of us know, President Obama intends to cut NASA's funding to such an extent that the Constellation project is going to be cancelled. What is implicated in this decision is the fact that it will leave the USA without any space vehicle of any kind to get into space. This means the...
  25. F

    Negative Magnitude Phasor Presentation: Is Erasing the - Sign Correct?

    If you have a phasor that has a negative magnitude (ie -3<38degrees) what is the best presentation. I believed it was just erasing the - sign and adding or subtracting 180degrees. Correct me if wrong
  26. G

    When to use negative sign ? [3 equations of motion]

    Homework Statement Example 3.13 : Example 3.1 Homework Equations v=u+at S=ut+1/2at2 v2-u2=2aS The Attempt at a Solution I know the solution is in front of me, that's ok but I have a confusion regarding negative & positive signs. In both the examples something is moving vertically upwards...
  27. I

    Physics/Chem: Why the sign difference in Thermodynamics?

    I have been wondering why we take work done on the system +ve in chemistry while -ve in physics. Similar difference exist for many other quantities. Can you explain why the difference exists?
  28. J

    The two meanings of the integral sign

    The integral sign \int can have two meanings: (1) It indicates the Riemann sum, in which we don't actually integrate, but add the rectangles under the curve. (2) It indicates the actual integration, in which we integrate (i.e. antidifferentiate) the function, either just to find the...
  29. N

    Differentiation under integral sign

    Homework Statement I have to evaluate the numerical value of the derivative of the following integral for x=1 \int_{0}^{\ ln\ x}\ e^{\ -\ x\ (\ t^2\ -\ 2)}\ dt Homework Equations The formula for differentitation under integral sign. The Attempt at a Solution The upper limit...
  30. pellman

    What does the triangle equals sign mean?

    Looks like \triangleq. I first came across it on the wikipedia article for Lie derivative. http://en.wikipedia.org/wiki/Lie_derivative#The_Lie_derivative_of_a_function
  31. N

    Neon sign, transformer failure

    Hi all- Can anyone offer any insight into a problem I've noticed for years but don't know how to solve? I'm a self taught neon tube bender. I am not an electrician or electrical engineer. Through the years, I've noticed neon tube, fluorescent lamp, transformer and ballast failure more often...
  32. T

    Trivial sign problem Please set me straight

    I'm calculating the capacitance of a set of spherical shells of radii b > a. To do this, I place a charge +Q on the inner shell and -Q on the outer shell so that I get the electric field vector pointing outward \vec E = \frac{Q}{4\pi\varepsilon_0} \frac{\hat r}{r^2}. Finding the...
  33. A

    -ve sign in expression of induced emf

    -ve sign in expression of "induced emf" What is the concept behind putting negative sign in: e=-[rate of change of flux] Which direction does it signify?? How does direction affect the equation? How and where can we use negative sign in other expressions of induced emf??
  34. L

    Understanding the Telegan Law: The Role of Double Summations in Power Analysis

    the telegan law basically states that the total sum of power is zero. my prof proved lik this: we choose a node (a point where more then one currents come together) and decide that the voltage on that node to be zero. we designate the voltages on the nodes to be e_k J_k is the current...
  35. M

    Determine the sign of angular momentum

    Homework Statement A 2 kg disk traveling at 3 m/s strikes a 1 kg stick of length 4 m that is lying flat on nearly frictionless ice .Assume the collision is elastic and the disk does not deviate from its original line of motion. Find the translational speed of the disk, the translational...
  36. C

    Spontaneous Expansion of Gas into Evacuated Container: Thermodynamic Analysis

    Homework Statement A gas spontaneously expands into an evacuated container. Indicate whether delta T, delta E, delta H, delta S, q, w, and delta G are positive, negative, or zero. Homework Equations delta G < 0 (spontaneous) delta G= delta H - TdeltaS delta E= q + w [/B] The...
  37. P

    Making 4'x8' sign inkjet printer - need nozzles - help?

    Hi all, hope I'm not intruding or posting in the wrong place, and I apologise in advance if I have. 1st, I am not a grad student, simply a guy with the desire to invent things and fix stuff till it's broken. A few of my projects include a solar tracking system, which analyses webcam images...
  38. J

    Solving for x with a Square Root Sign: Help Needed!

    Does anyone know how to solve for x in the following equation: x + \sqrt{x} = 6 I don't know how to solve for x with eq'ns like this, and I'm studying inverse fxns right now, so I'm told that's what I'm supposed to do. The square root sign is throwing me off. The first time I tried...
  39. S

    Calculate Impact Speed of Car Hitting Sign

    Hi, I hit a 4x4 post holding a streetsign up on a country road. I guess I was doing about 20 or 30 when I went off the road and struck the sign. It snapped the 4x4 in half at impact point and then toppled onto and almost into my windshield. I am looking for a physics formula to help...
  40. E

    Sign of voltage across inductor

    I need help understanding the sign of voltages across an inductor. Homework Statement There is a current source providing current I to a resitor of resistance R in series with an inductor of inductance L, of which the other end is grounded. The voltage at the current source is V1 and the...
  41. P

    A general way of determining the sign of work?

    Good evening, (NOTE: This post got a little long; I hope someone has enough patience to read it.) I self-teach physics to myself, but I don't have a complete book (I only have "Volume 2: Gravity, Waves and Thermodynamics" of "Physics" by Paul Tipler). Volume 1 discusses work and energy, but...
  42. L

    Help with Sign Reversals in Solving Quadratic Inequalities

    Homework Statement Here are two, unconnected example problems, having to do with quadratic inequalities. I'm confused b/c I understand how to solve them with an = sign, but as inequalities the book shows extra steps where signs get reversed and a total of ~ 4 possible answers come up instead...
  43. G

    Attempting to retrieve painted image from rusted galvanized sign

    hello. I am wondering if there is anyway to retrieve a painted image from a galvanized sign that has rusted over. The original logo/name was likely painted in black stencil over galvanized sheet metal. I have not seen it in person yet, but from pictures it looks like image is gone and whole...
  44. L

    Mastering Coulomb's Law: Troubleshooting Sign and Distance Issues

    [b]1. Homework Statement [http://img44.imageshack.us/img44/1104/58339946.jpg ][/URL] [b]2. Homework Equations [F=k*abs(q1)*abs(q2)/r^2] [b]3. I understand the equation, but I am having trouble with my signs and also how to include the distance in the equation. I know that the...
  45. S

    Fouier series from the sign function

    Homework Statement If I have the standard sign function defined on R is the corresponding Fourier series the standard Fourier series with plus/minus in front respectively? Homework Equations The Attempt at a Solution
  46. C

    Solving for Tension in a Suspended 28kg Sign

    Homework Statement Attached is a diagram of the problem. A 28kg sign is suspended by two massless cables. Find the tension in each. Homework Equations The Attempt at a Solution I'll call the cable at 57 degrees T1 and the other cable T2. T1∙cos 57 + T2∙cos 36 = 9.8m/s2∙28kg T1∙cos 57 +...
  47. C

    Do All Circuit Elements Follow the Passive Sign Convention?

    Homework Statement 1) Q. Which of the elements follow the passive sign convention? (psc) http://img401.imageshack.us/img401/3092/pic1r.gif v1 = +5 (V) i1 = +2 (mA) v2 = -10 (V) i2 = +500 (µA) v3 = +1 (V) i3 = -3 (mA) 2) Q. Which of the elements follow the passive sign...
  48. P

    Why is the difference in electric potential negative?

    Homework Statement Why is the difference in electric potential between points A and B defined as the NEGATIVE of the work done in moving a test charge along the path from A to B and then dividing by the charge q? Why the negative sign? Just wondering. Homework Equations Delta V = -...
  49. M

    Sign problem in laplace transform

    Homework Statement \int_{\pi/2}^{\infty}cos(t)e^{-st}dt Homework Equations \int vdu=uv-\int udv v=cos(t) , dv=-sin(t)dt , du=e^{-st} , u=\frac{-e^{-st}} {s} The Attempt at a Solution \int_{\pi/2}^{\infty}cos(t)e^{-st}dt = \frac{-e^{-st}}{s}cos(t) -\int...
  50. M

    Domain of a Function with Sign Graph

    Homework Statement Find the domain of the function. You will need a sign graph. Answer in interval notation. Homework Equations f(x)= (3)/[(x2-4x)1/2] The Attempt at a Solution No clue - I don't know how to use a sign graph or what the positive/negative results mean as solutions on a number line.
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