Sign Definition and 596 Threads

What is the rationale for the sign convention in the space-time 4-vector? How is it related to the sign convention in the energy-momentum 4-vector, if at all?

Homework Statement The temperature T at a location in the Northern Hemisphere depends on the longitude x, latitude y, and time t so we can write T=f(x,y,z); time is measured in hours from the beginning of January. Honolulu has longitude 158 degrees W, and latitude 21 degrees N. Suppose that...

Homework Statement The value of the Electric field at a distance of 82.8 m from a point charge is 75.3 N/C. Its direction is radially in toward the charge. The Coulomb constant is 8.98755 E9. Find the magnitude and sign of the point charge at the origin. Answer in units C. Homework...

Another group of strong pictures for this contest. Please vote for the picture that best represents our theme, which is on signs. 1. hypatia 2. alex_caps http://img174.imageshack.us/img174/6237/signckqx9.png 3. matthyaouw 4. Mech_Engineer 5. ZapperZ...

the 'not equal to' sign ( =/= )? If I say, blue =/= red. could you simply say: blue = 0 red? Or: life =/= death... mean life = 0 death? Does the not equal to sign mean merely 'incompatible' or does it mean 0 of the thing =/=? How do you use that sign?! I may be far off

Homework Statement A girl of mass M stands on the rim of a frictionless merry-go-round of radius R and rotational inertia I that is not moving. She throws a rock of mass m horizontally in a direction that is tangent to the outer edge of the merry-go-round. The speed of the rock, relative to...

[SOLVED] Sign Convention - Physics - Optics I was just looking at some sign conventions and I was wondering if this is true: Along the principle axis, if Si > 0, then does that mean you have a real, inverted image? Also along the principle axis, if So < 0, then does that mean you have a...

[SOLVED] Tension- Hanging Sign A 20.0 kg sign is being held up by 2 ropes. Each rope makes a 60 degree angle with the sign. So there is an upright triangle, each angle 60 degrees. I have to calculate the tenstion in the two ropes. So far, I have \Sigma F_{}y=ma_{}y +Fa_{}1sin60 +...

Hey guys, I need some help clearing up voltage signs, its always confusing me and I have my final this Friday. First off I'm not talking about voltage in a circuit, but rather if there is an electric field caused by a charge distribution. First off, I understand potential energy for gravity...

[Solved] Where did I go wrong? \int \frac{(x-2)}{x(1+x^2)}dx \int \frac{x}{x+x^3}dx - \int \frac{2}{x+x^3}dx I choose u = arctan(x) so du = \frac{1}{1+x^2} and \int \frac{x}{x+x^3} = \int \frac{1}{1+x^2} 1) \int \frac{1}{1+x^2}dx = arctan(x) 2) \int...

At the top of their 50 foot tall sales building, there is a 10 feet tall sign. But he wants to replace it with a sign for which the ideal viewing distance is 60 feet from the building. For an observer, the angle between the lines of sight from the observer's eye to the top and the bottom of the...

Occasionally I get administrator emails that indicate emails bounced back. The email is some spam thing. It looks for all the world like I sent that piece of spam, though I have the latest spam blocking s/w. Does this, in fact, mean that my system is affected, or is it a fake?

Homework Statement There is a sign of mass M that is attached to a rigid bar perpendicular to the ground. There is also a rope attached to the sign at the same point, then pulled out at an angle 45 degrees below the horizontal up to the ceiling. a) Consider the rigid bar to be at...

Please provide me with some help in optics. This doubt is in relation to the use of sign conventions in optics. Whenever we prove anything in optics, say for example, when we prove the mirror formula or the lens formula or the lens-maker's formula, we apply the sign conventions in the derivation...

As we have seen some mathematical sign lately in this group, because I put you in the drawing of the general sign of any element. You also can see more searching “from zero to infinite, ferman”. Thank you.

Homework Statement Two large, parallel, conducting plates are 12 cm apart and have charges of equal magnitude and opposite sign on their facing surfaces. An electrostatic force of 3.9 \times {10}^{-15} N acts on an electron placed anywhere between the two plates. (Neglect fringing.) (a)...

Homework Statement If you are hanging a sign from the ceiling with two wires, each with a safe working load of 20N. The hooks at the top of the sign are 2.0 meters apart while the hooks in the ceiling are 4.0 meters apart. A) If the sign weighs 30N what is the minimum angle to the horizontal...

What does it mean when an op amp has only a minus sign in its symbol? Is the positive terminal at ground, or is it at some arbitrary voltage?

Homework Statement Hans stands at the of the Grand Canyon and yodels down to the bottom. He hears his yodel echo back from the canyon floor 5.20s later. Assume that the speed of sound in air is 340.0m/s. How deep is the canyon at this location? I made a chart. Velocity Original = 340...

Homework Statement 4. In Fig. 23-28, a butterfly net is in a uniform electric field of magnitude {E = 3.0} mN/C. The rim, a circle of radius a = 11 cm, is aligned perpendicular to the field. The net contains no net charge. Find the electric flux through the netting...

I'm working on this hanging sign problem: A sign hangs precariously from your prof's office door. Calculate the magnitude of the tension in string 1, if θ1 = 27.42°, θ2 = 67.35°, and the mass of the sign is 9.9 kg. I was wondering if I could put 9.9*9.8 as a leg in the middle of the...

Hi all. Say, I have an alegebric function, e.g. f(y;a)=y^4+b*y^3+c*y^2+d*y+e, where the coefficients b,c,d and e are all depends on a single parameter, a. What I want to do is to check what is the condition of a for the function f(y;a) to change its sign between 0 and 1+a, do you have any...

Please help! This is urgent! Homework Statement 1) A typical car's brakes can create a maximum acceleration of less than 5 m/s^2 . How close can you get to a stop sign before you start braking? Homework Equations no idea at all since there isn't even enough information given to solve...

What does an equal sign with a straight line down the middle of it mean?

Hello: I need help determining if I and V assignments follow the passive sign convention. Here is the image of the circuit: http://img178.imageshack.us/img178/9572/pic1xu2.gif I know that in order for it to follow PSC the current I needs to flow towards +V. I'm not sure if that is...

Latex - how to get non-italic UK "pound" sign I'm using MikTex. When I do \usepackage{times} and then use \pound or \textsterling in non-maths mode, I get the italic version of the "pound" symbol from the Times Roman font. I want a non-italic pound symbol. I also get this message in...

Homework Statement How come it is said that attractive forces such as gravitational force have negative sign? And how come the sign is ignored in the case of gravitational force? And also, how come gravitational potential energy carries a negative sign? Is it because the displacement of the...

I have a hard time trying to derive the equation in 6.4 . This is what I've done, and as you will see I have a sign difference compared to his. http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PRVDAQ000070000001015012000001&idtype=cvips&prog=normal Starting with page 8...

Would obviously synthetic particles traveling through space be a choice to broadcast the presence of life? Likewise, say we detected an unnaturally large cross section of an otherwise rare particle impinging upon Earth; might that vestige be a purposeful indication of extraterrestrial civilization?

at the bottom of a post? i mean your userid is just to the left of the post? is it so that if someone murders you and tries to infiltrate our ranks we'll know? maybe it's because some of you write such long posts that by the time one reads the whole thing scrolling up is counterproductive? bob

hi. 1. Why does the sign of the metric have to be (+,-,-,-) or (-,+,+,+)? meaning why does the sign in front of the time part of the metric have to be different than the signs in front of the spatial part of the metric? is there a good answer for this question other than it gives the right...

To clear up the confusion of signs to use for mirrors and lenses. Would this be a correct way of memorizing the signs? For the equation: 1/s_o+1/s_i=1/f Mirrors: Concave: Since light actually converges at the focal point, it's positive. Any image that is on the same side as the focal point...

i am studing physics and i Sign up for this courses and I think it is to much: 1st year: Introduction to physics I Introduction to physics II Mathematic (matrixes) Mathematic (Calculus & Analysis) Mathematic (matrixes & Vectors) Mathematic (probability theory) Introduction to chemistry...

the material is over coulombs law, and i am having a rough time understanding the business of the sign's of the charges and the direction of the charge at the same time. here is a problem from the text.: Two charges are located on the x-axis with q1 = 2.3 x 10^-8 C at the orgin, and with q2...

Homework Statement a.) What is the lowest number represented by a 12-bit machine using Sign Magnitude? b.) What is the largest? c.) What decimal number does the bit pattern "101001010010" represent?Homework Equations For a and b: Signed integer ranges for N bits (I don't know if this is...

Homework Statement 1)I have a doubt regarding the sign of g factor value. In Wikipedia the g-factors are given as: Orbital g-factor Mu(L) = g(L)[Mu(B)L]/h_bar Where g(L)=-1 is the orbital g factor Spin g-factor Mu(S) = g(S)[Mu(B)S]/h_bar Where g(S)=-2 is the spin g factor Lande...

Homework Statement This is ralated to completely monotone functions. if a function and its successive derivative changes sign then what does this mean? Homework Equations The Attempt at a Solution

minus sign in "forces in space" problem. Homework Statement see picture for problem. Homework Equations please see a picture (one is of problem, the other contains the relevant formula). The Attempt at a Solution I was able to solve the whole thing, then looked at the solution...

Hi, Let L be an inductance, then you find the following formula in textbooks (high school level): U_ind = - L dI/dt When you actually do calculations for circuits, you see that the minus sign is wrong. So why do they put it there?

I guess this is more of an anthropological post. Is there any pattern to which sign convention people prefer? Or is it just a matter of which you were exposed to first?

Electrodes in cells usually have a sign of either + or - My textbook talks about the + as because the electrode is positively charged and - when negatively charged. But is that correct? The electrodes are meant to be conductors and shouldn't be charged at any time. When they do, the ions...

Hi, I have posted this doubt in other forums and people don't know the answer. (sorry if my English is not very good!) Let's see: to obtain the operator for the magnetic moment component of a particle, we have to apply a few factors to the spin operator, and one of them, the so-called...

This is my (error full?) understanding from my readings: 1. positive current flowing into a positive terminal of let's say a rechargeable battery is power being absorbed by the battery...so positive watts 2. negative current flowing into a positive terminal encounters the higher electrical...

Homework Statement http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam1/fa06 Homework Equations W =F*D The Attempt at a Solution I have it solved, now i thought - would be if i put work into the thing to move it but looking at it since both of...

If you have two blocks connected over a pulley, and are using the torque on the pulley to calculate the acceleration, then you should disregard the sign of the torque, always treating it as positive, no matter which direction it rotates? Is this right? Thanks, Dorothy

Sometimes the following symbols are used instead of an equal sign. I think the single one ~ means "is proportional to". One of the other ones means "is approximately". Which one is it? I'm guessing the second one because LaTex calls it approx. When are the others used? \begin{array}{l}...

I have been having a really rough time on my 3 homework problems tonight...I don't really understand vectors, so any help would be appreciated! Sorry about the no LaTeX, I don't know how to do the vector sign:confused: Anyway... 1.Given the Vectors U=2i(hat)-3j(hat)= <2,-3> and...

I know Kirchoff's 2nd law but when applying to an electrical circuit i am bit confused :confused: with taking correct signs for emf,product of resistor & currect etc. Anyone please help me to solve problems related with Kirchoff's 2nd law in an easy way.

Hi. Okay, this has been driving me crazy. When combining two given waves into a standing wave equation, how do you know which sign to put in front of the amplitude? All the examples I've been finding seem to contradict each other. Here are three examples from my textbook: 1. Incoming Wave...

Hi there, We are about to use that sigma sign in chemistry we have however not got told about it in math. SO therefore I am asking you if you could give me a brief introduction to it and how to use it and etc.