Reference Definition and 1000 Threads

Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to refer to the second object. It is called a name for the second object. The second object, the one to which the first object refers, is called the referent of the first object. A name is usually a phrase or expression, or some other symbolic representation. Its referent may be anything – a material object, a person, an event, an activity, or an abstract concept.
References can take on many forms, including: a thought, a sensory perception that is audible (onomatopoeia), visual (text), olfactory, or tactile, emotional state, relationship with other, spacetime coordinate, symbolic or alpha-numeric, a physical object or an energy projection. In some cases, methods are used that intentionally hide the reference from some observers, as in cryptography.References feature in many spheres of human activity and knowledge, and the term adopts shades of meaning particular to the contexts in which it is used. Some of them are described in the sections below.

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  1. M

    Breit Frame of reference ( Brick Wall )

    Breit Frame of reference ("Brick Wall") I am having a lot of trouble understanding breit frame of reference.I was trying to solve griffiths problem 3.21 (1st ed.): Consider elastic scattering- A+B----->A+B If particle A carries energy E, and scatters at an angle theta in the CM, a) what is...
  2. f95toli

    Private communication (as a reference)

    I have a question about the correct way to write a reference to a private communication. The other day I was making some corrections in the proof of an article that will soon be published. One of the questions/comments from the editors office was that regarding a referenfce to a private...
  3. S

    Kinetic friction in an accelerating Frame of Reference

    Can the kinetic friction be in the direction of acceleration? I am thinking of the example of a box on a flatbed truck accelerating to the right from rest. The box accelerates to the left due to the inertial force as seen by an observer on the truck where the kinetic friction is opposite to the...
  4. L

    Boat crossing river problem using reference frames

    Homework Statement A 110-m-wide river flows due east at a uniform speed of 3.3 m/s. A boat with a speed of 8.6 m/s relative to the water leaves the south bank pointed in a direction 37 degrees west of north. What is the (a) magnitude and (b) direction of the boat's velocity relative to the...
  5. E

    Kinetic Energy and Frames of Reference

    From what I can glean, since kinetic energy = 1/2 mv^2, it follows that a doubling of velocity requires a quadrupling of energy. One joule is required to accelerate a 1 kg mass from zero to one meter per second per second. ie 1m/s2. Now, to further accelerate the mass to 2 meters per second...
  6. U

    Looking for reference on hot pressing

    Hello all, I am conducting some experiments in which the samples are to be produced via hot pressing. However, I have been unable to produce flaw-free parts (e.g., parts exhibit pancaking and crown defects). I'm not sure what modifications to the load schedule or die assembly should be made...
  7. B

    Are laws of nature really the same in all reference frames?

    Let’ say; “A” can see and measure a stone falls to the Earth let’s say 10 meter per 1 Earth-second. “B” lives at Mercury and can see the same thing. But “B” would do not see the exactly the same, because seen from “B’s” viewpoint time / distance is not the same as for “A”. Let us say...
  8. W

    Frames of Reference and Relative Velocity

    A swimmer who achieves a speed of 0.75 m/s in still water swims directly across a river 72 m wide. The swimmer lands on the far shore at a position 54 m downstream from the starting point. (a) Determine the speed of the river current. (b) Determine the swimmer?s velocity relative to the shore...
  9. C

    Susskind Lecture - accelerate reference frames

    in at 0:47:00 Susskind begins discussing accelerated reference frames and notes that they relate to hyperbolas rather than parabolas. I understand the concept and need for the proper acceleration to be asymptotic at C. Susskind seems to infer that an observer in the accelerated frame will...
  10. C

    A simple physics problem [frame of reference]

    A large heavy box is sliding without friction down a smooth plane of inclination Ɵ. From a point P on the bottom of the box, a particle is projected inside the box. The initial speed of the particle with respect to the box is 'u' and the direction of projection makes an angle α with the bottom...
  11. R

    Why is my sensor output only 1v when using a 2.5v reference voltage?

    I have sensor that produces differential output. I saw in the sensor schematic that they have used 2.5v DC as reference in the output minus terminal. I am taking sensor output as differential that both positive and negative(2.5DC ref terminal)in count. I got output as 1v of DC when the sensor is...
  12. C

    Good Multivariable Calculus reference text

    What is a good, solid reference text for multivariable calculus? Ideally something you'd get by following on from Spivak's Calculus into 2/3d/Vectors etc. I've already done the course, but it's sort of slipping my mind these days - I've mostly been doing chemistry subjects, and they're not...
  13. K

    What Are the Best Thermodynamics Books for IIT-JEE Preparation?

    Hi, I am a grade 11 student preparing for the IIT-JEE. I would like to know about some good books on thermodynamics. Young, Sears Zemansky & Resnick/Halliday/Walker don't go into much depth on this topic.
  14. P

    Rotated Reference Frames and Angles/Accelerations

    Homework Statement Let's say that there is a bicycle traveling forward and we only see it from behind. As it rolls to turn, it induces some accelerations. If we were to measure those accelerations on the bicycle frame itself, we would see a Lateral Acceleration (lets call it Aym) and and a...
  15. K

    What are the best reference books for IIT-JEE Physics?

    I'm a Grade 11 student preparing for the IIT-JEE. Can anyone suggest me good reference books for PHYSICS? I looked up H.C. Verma but did not find it appealing at all.
  16. K

    What Are the Best Reference Books for Physical Chemistry for IIT-JEE?

    I'm a student preparing for IIT-JEE. Can anyone suggest me some standard reference books for physical chemistry?
  17. Y

    How can I access to the following reference?

    V. A. Belinskii and V. E. Zakharov, Integration of the Einstein Equations by the Inverse Scattering Method and Calculation of Exact Soliton Solutions, Sov. Phys. JETP 48, 985 (1978)I cannot access to in via the library in my department. But I need it in my research. Sad...The website...
  18. jaketodd

    Speed of Gravity the Same in All Reference Frames?

    I found this article: http://www.csa.com/discoveryguides/gravity/overview.php" The article says gravity moves at the speed of light. But does gravity do so in any reference frame, like light does? Thanks, Jake
  19. M

    Reference for a full list of John von Neumanns publications.

    Hi, I' am wondering If someone knows a reference for a full/complete list of John von Neumanns publications. I have been unable to find one, but something like that should really exist right? thanks for the help in advance Oh and I am not sure whether this is the right subforum, but it...
  20. T

    I can't find this reference (Wheeler, N. A.)

    During the D.J. Griffiths, Introduction to Elementary Particles, the author introduces unpublished references "Classical Chromodynamics" and "Bare Bones of the Classical Theory of Gauge Fields", Reed College, Portland, O.R. which is written by Wheeler, N. A. (1981). Where can I find this...
  21. G

    Dissertation supervisors - reference quality vs quality of supervision

    I am wondering who to ask to supervise my dissertation (I'm in final year undergraduate mathematics). My interest is functional analysis and there two members of staff involved in this area. X is a professor and he is well respected, Y has been a lecturer here for about four years and is well...
  22. M

    Penrose diagrams, reference request.

    Where can one find a general and detailed exposition of Penrose diagrams? What I have seen so far, in the books, are relatively brief general comments and a couple of specific examples. Usually Minkowski and Schwarzschild metrics, sometimes one or two more.
  23. N

    Conservation of energy in ALL frames of reference?

    If all frames of reference are taken as equally valid. when a car moves, to the passengers in the car the world is moving in the opposite direction. Moving the whole world should take a lot more chemical energy than was contained in the gas that was burnt... I know the passengers in the car...
  24. D

    Is planck time the same in all reference frames?

    Quick question: Is Planck time the same in all reference frames? Is it different at, say, half the speed of light than at a relatively stationary point? What about in a severe gravitational field, like a black hole?
  25. S

    Speed of sound, frames of reference

    Homework Statement [PLAIN]http://www.antonine-education.co.uk/Physics%20A%20level/Options/Module_8/Topic_6/cars_4.gif What is the speed of sound, relative to: A - B - C - Homework Equations None. The Attempt at a Solution For B, since B is a stationary reference point...
  26. L

    How Do Moving Charges Behave Differently in Different Reference Frames?

    Consider two point charges in space: one positive(+Q) and other negative(-Q), lying on the y-axis and separated by distance 'r'. In frame A, both charges are at rest so, only attractive electrostatic force (F_elec) acts on both the charges which is defined by coulombs formula. In another frame...
  27. M

    Pi Measons - frame of reference

    Please help, I am confused with part c and d. 1. Doug in a lab on Earth observes a π-meson is created 2.8 km from the surface of the Earth. It has a rest decay time is 9.0 x 10-6 s and it travels straight down to the Earth at 0.95c. a) What distance would the π-meson measure to the lab...
  28. A

    Quick question about inertial frames of reference

    Homework Statement If you are on the merry-go-round going in a circle at constant speed, are you looking at the world in an inertial, or non-inertial frame of reference? How do we tell whether from one's viewpoint, they are looking at something from an interial or non-inertial frame of reference?
  29. D

    Poission equation, spherical harmonics, looking for reference

    Hi folks, I'm looking for a derivation of the following statement (formula 76) http://img845.imageshack.us/img845/1550/screenshot4op.png Do you know any reference, where I can find a bit more detailed description? I reckon, you can find it in Jackson's electrodynamic book, but I couldn't find...
  30. W

    Can someone explain non-inertial reference frames

    What is a non-inertial reference frame? how is it defined?
  31. G

    Physical definition of inertial reference frames

    Dear all, I'm trying to understand better why gravity makes impossible to physically define an inertial reference frame. Firstly, we must have an operational procedure that allows us to physically define an inertial reference frame. Secondly, we must show that gravity makes this procedure fail...
  32. R

    Can Special Relativity Explain Accelerating Reference Frames?

    So apparently SR can handle non-inertial reference frames, and there are supposedly some interesting effects that come about, like non-constancy of the speed of light. I was wondering if anyone knew where I could find a treatment of accelerating frames in SR (like a textbook)?
  33. Z

    Exploring Inertial Reference Frames in the Expanding Universe

    Are galaxies, quazars inertial reference frame? I think they are at rest or moving at constant velocity relative to the expanding space. But what is the coordinate system to the scale of the whole universe that can describe these inertial reference frames appropriately? Is the coordinate...
  34. Q

    Magnetic dipole in two reference frames (special relativity problem)

    Homework Statement An EM wave traveling in vacuum has a magnetic field in the lab frame K which is given by \vec{B}(\vec{x},t) = \hat{z} B0 \cos{kx-\omega t} where Bo, k are positive constants and omega = ck. a) A point magnetic dipole, m, where m = \hat{y}m0 (m0 constant) is at rest in...
  35. L

    Understanding Bandgap Voltage Reference Circuits

    I am not able to understand how a bandgap voltage reference works. The simplest ckt I found was here - (figure 2) - http://www.national.com/rap/Application/0,1570,24,00.html You have 2 branches of diodes, in one branch rich (high) current flows and in the other lean (small) current flows...
  36. M

    Calculating Euler Angles from Two Frames of Reference

    Fairly straight forward question. If you have a set of three vectors specifying a frame of reference and a second set of 3 vectors stating another frame of reference. How do you get the Euler angles associated with that rotation? More generally I am considering the relative orientation of one...
  37. S

    Can an Inertial Frame Stop a Constantly Rotating Object?

    If a solid object rotates at constant angular velocity, is it possible to chose an inertial reference frame in which the object will not rotate?
  38. Hepth

    An online reference for SM Feynman Rules?

    I'm not always on the same computer, often times I'm using my phone to look for answers when doing physics on the go. Does anyone know a good, correct resource for ALL of the tree level feynman rules for QED+EW+QCD? Feynman gauge would be preferred, or ungauged. I can find most for the...
  39. D

    The Twin Paradox: Mike & Angela's Frame of Reference

    I am confused about the twin paradox. Let's imagine Mike and Angela are twins. Mike stays on Earth, and Angela rockets off, away from Earth at close to the speed of light, with the intention of making a round trip back to Earth at the end of her voyage. My question is this: why wouldn't...
  40. T

    Help with special relativity (frames of reference)

    Well I've just been learning about special relativity, and I think I understand everything I need to know, except frames of reference (for A level). I need to know where you are allowed to take frames of reference from, and where you are not. I understand that you can't take a frame of...
  41. J

    Need reference or derivation of Gamma function for half-integer orders

    Hi all, I'm looking at the http://en.wikipedia.org/wiki/Gamma_function#General" for the gamma function, and it lists equations for the gamma function of half-integer orders (i.e. gamma(0.5+n) and gamma(0.5-n)). But, it doesn't list a reference as to where this equation comes from. Does...
  42. Y

    Is there any good reference of tetrad in GR

    I want to find a good reference in GR about the application of tetrad. Is there any good suggestions?
  43. M

    What's an inertial frame of reference?

    The Earth is an approximately inertial reference frame since it's acceleration with respect to the stars is very small. But if a group of stars is accelerating with respect to another group of stars which group is the inertial frame? Or thinking on an even larger scale, if a universe is...
  44. Jonnyb42

    How are Christoffel symbols different in rotating reference frames?

    A very important idea in General Relativity is, same laws in all reference frames. How does that work in rotating reference frames? Jonny
  45. L

    Do you have a personal reference book? Share tips on creating one!

    (feel free to move this post if it doesn't belong here) I've been searching around the internet and here for the past few days and can't find anything relating to this. Does anyone keep a personal notebook wherein they have complied useful formulas and such for reference? If so I would...
  46. M

    The part of relativity I never got, reference frame

    So I was pondering long distance space travel. As I understand it, if you can accelerate a vessel, say over the course of a year, to near light speeds, you can cover very very long distances in a very short period of time(as measured on your on space ship) due to the effects of relativity...
  47. P

    Without paging only 1 memory reference is required

    "suppose there is an instruction to copy one register contents to another... now, without paging only 1 memory reference is required to fetch the instruction...but with paging..we need 3 memory reference (as page tables are to be accesed)..." please explain why 3...?
  48. D

    How Do You Calculate Electric Field for a Non-Parallel Finite Line of Charge?

    Homework Statement Last week I https://www.physicsforums.com/showthread.php?t=483819" which I believe didn't get answered because my description of the problem was a lot messier than it needs to be. Hopefully today, I will not make the same mistake. In physics books, when calculating the...
  49. L

    Space Probe vs the Sun - Relativistic Frames of Reference

    I've had a good search through the archives and haven't found an answer to this question. Many apologies if this is old ground. . . Having read the threads on the Pioneer Anomaly a quick question to which I'm sure there is very simple answer (I just don't know what it is !): When...
  50. K

    Reference points in a moving system

    Homework Statement I have been looking at one of my review sheets, and do not know how the professor got the equations. Here is the relevant paragraph: Consider two particles of mass m1 and m2 isolated within a box, with respect to which they have velocities u1 and u2. The box is moving at a...
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