What is Reference: Definition and 1000 Discussions

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. N

    Rest Mass and Preferred Frame of Reference

    Einstein's theory of relativity is based on the fact that all motion is relative, which precludes the existence of a universally defined state of rest (priviledged reference frame). Einstein also recognises the existence of rest mass. If an object were at its rest mass, wouldn't it be perfectly...
  2. F

    Question about rotation and reference

    Hi. Let's suppose to have a car with a reference system called Body-NED with its origin in the center of gravity of the car, Xb-axis (called North) pointing towards the front of the car, Yb-axis (called East) pointing towards the right door and Zb-axis (called Down) pointing...down the street...
  3. S

    Inertial and non-inertial frame of reference

    Okay, so I know what inertial and non-inertial frames of reference are: 1. Inertial is when Newton's laws of motion hold. 2. Noninertial is when they do not hold (the object is accelerating without a force). And I have a few examples as well, such as when you are is in a car and the car is...
  4. P

    What is Energy with reference to Human energy and attraction of earth field.

    Human body is mass having energy. thanks to Joule it is proved. Newton explained First, Second and Third laws. Now, 1. Two equal amount of forces in opposite direction at a given time may not move the OBJECT as per third law of Newton. This is horizontal pull like Tug-of-War. Here 'x'...
  5. S

    Frame of reference, energy and momentum of particle

    Homework Statement In a certain reference frame, a particle with momentum of 4 MeV/c and a total energy of 5 MeV (a) Determine the mass of the particle. (b) What is the total energy of the particle in a reference frame in which its momentum is 4 MeV/c? (c) What is the relative speed of the two...
  6. J

    Reference for diamagnetic vs paramagnetic

    I am not a chemist, so I have a feeling I'm going about searching for the wrong key words or something. What I want is a table of Fe+2 and Fe+3 compounds in solution (ie. different ligands like CO, CN-, etc.), listing each compound as paramagnetic or diamagnetic. I've searched for a nice...
  7. G

    What's a natal kick in reference to astrophysics?

    I'm reading a research paper and they bring up the term "natal kick". And google didn't turn up a great explanation immediately so I thought I'd check here. Can anyone help me? Thanks.
  8. E

    Photons & Frames of Reference.

    I accept that the FAQ section is there to cut down on repetitive questions, but this arises out of an answer in the FAQs. Would this line of reasoning not lead to the conclusion that, even without an inertial frame of its own, a photon would not be able to be stationary relative to itself?
  9. M

    From what frame of reference does the Earth orbit the sun?

    I have been doing some study on the theory of relativity and it has got me thinking. We say that the Earth revolves around the Sun but from what reference frame? From the reference frame of Earch, we are stationery and the Sun simply spins. Why is any reference frame more accurate than another...
  10. T

    Special relativity question - reference frames

    Homework Statement Suppose that A', B' and C' are at rest in frame S', which moves with respect to S at speed v in the +x direction. Let B' be located exactly midway between A' and C'. At t'=0, a light flash occurs at B' and expands outward as a spherical wave. 1. According to an observer...
  11. 1

    Reference Angles: Find the Angle of $\frac{7\pi}{6}$

    Homework Statement Find the reference angle of - \frac{7\pi}{6} Homework Equations - The Attempt at a Solution I can tell you right now, that the answer is pi / 6. My method would be to sketch the angle, find out at which point the appropriate x axis-coordinate will be used...
  12. N

    Is it possible to reference Lemmas inside another Lemma?

    Homework Statement Is it possible to reference Lemmas inside another Lemma? That is, while you are trying to prove a lemma, you refer to another lemma you have just proven. Is this accepted? Homework Equations None. The Attempt at a Solution None.
  13. K

    Reference for scalar-vector-tensor decomposition of perturbations

    Hi... Can anyone one give me a good reference for the decomposition of perturbations into independent scalar, vector and tensor parts, with all the gory details?
  14. E

    Does a photon have a frame of reference?

    My thinking has been that a photon, in its own F of R, in a vacuum, travels through space, but not through time. This seems to have been "confirmed" in various things I have read. However, I recently came across the assertion that "...in physics, there is no theory that defines the frame...
  15. U

    Relative acceleration between intertial reference frames?

    Does special relativity hold between two inertial reference frames that are undergoing relative acceleration? For example, consider two spaceships traveling toward each other on parallel (but not collinear) trajectories. They would pass each other at some non-zero distance, and thus their...
  16. R

    Ignore voltage reference on resistors?

    I'm working on 3.19 from Schaum's Outlines: Basic Circuit Analysis (not homework). The problem can be found at this...
  17. H

    Understanding the Reference Point for EMG Out Voltage

    Hello.. Am working for my FYP concerning prosthetic arm, so i have to take data from EMG sensors which are on the surface of the body. The first step of my project is signal conditioning and filtering, so i was searching for circuits concerning signal conditioning and i got the circuit in the...
  18. K

    Preserving Magnetic Polarity in a Revolving Reference Frame

    ***not homework for any class*** Title: "Preserving Magnetic Polarity in a Revolving Reference Frame" Problem: How can a revolving reference frame (assuming an uncharged observer with negligible mass) observe the same polarity for a magnet in the case where the rotational speed is great enough...
  19. N

    What is the best frame of reference?

    So I was studying some physics, and I keep encountering how many things depend on the frame of reference. For example, kinetic energy and momentum. My question is if there is an absolute frame of reference? Can we define one? I remember reading somewhere that the absolute reference...
  20. N

    Does light really travel in same frame of reference

    Hi, I have a simple question in my mind, I could not find the answer anywhere so I came here. Here is my question, Assume a source of light and observer are five light seconds apart, and are travling parllel to each other at a constant speed of say 200 meters per second. Now if the source of...
  21. L

    SR, electromagnetic waves in moving reference frames.

    Homework Statement Not really a homework/coursework problem, I'm just trying to make sense of some class notes from our chapter on special relativity. I'm trying to find the expression for electromagnetic wave propagation in a reference frame S' that is moving at a constant velocity with...
  22. S

    Understanding Acceleration From Different Frames of Reference

    This is what my teacher told me, but I still don't really see how it works. Say a person is in a car traveling at constant velocity, and it crashes into a tree, from an inertial frame of reference (the road), the person in the car continues traveling at the constant velocity of the car until...
  23. W

    Cons. Angular Momentum & Reference Frames

    Hi! I'm currently a student taking a classical mechanics course. Finals are coming up, and I've come to realize that I seem to have a firm grasp of most of the material (energy, forces, etc...) but not momentum. I know this because I was flabbergasted by a problem on my last midterm that...
  24. Z

    Lorentz Transformations and Reference Frames Problem

    Homework Statement In the old West, a marshal riding on a train traveling 35.0 m/s sees a duel between two men standing on the Earth 55.0 m apart parallel to the train. The marshal's instruments indicate that in his reference frame the two men fire simultaneously. (a) Which of the two men, the...
  25. P

    5V to 5V precision voltage reference

    Is there any IC that can output a precision 5V from a 5V supply?
  26. J

    Calculating Drag (having circular reference problems)

    Homework Statement I don't know if it's possible but I am doing a physics EEI on drag. I know to find drag you need instantaneous velocity which can be found through (change in x/ change in t) but i cannot find displacement unless i find velocity :S.. Homework Equations d = 0.5 x p x...
  27. J

    How Do Rotating Reference Frames Affect Forces on a Merry-Go-Round?

    Looking down from a stationary tree branch, a merry-go-round spins in a counterclockwise direction with an angular velocity of 1 radian per second. a squirrel of mass 0.2 kg sits on the outer rim of the merry-go-round, at a radius of 2.0 meters. a) what is the magnitude and direction of the...
  28. P

    Precision 5V Reference: LT1085 vs LM317

    Anyone can suggest a very precise and constant 5V reference? I Google and see many are recommend LT1085 and LM317? Which one is better? Any better recommendation?
  29. J

    Inerital vs Non inertial reference frames: quick conceptual question

    Homework Statement I'm doing a problem in which an ant crawls in a circle on a spinning pottery wheel. Say I'm looking at the friction which holds the ant in place. It keeps the ant from slipping. Looking at it in the inertial frame of reference, I know that the centripetal force points...
  30. R

    A sliding puck analyzed from an inertial reference frame

    Homework Statement Located here:http://imgur.com/qP9fd.png" The Attempt at a Solution I don't know how to do this problem. First of all how do I approach it? Should I do a free-body diagram? Should it be done at position 1? How do I account for the different frame of reference...
  31. K

    Pendulum tension in rotating reference frame

    Homework Statement A student is in a rotating chair with a pendulum hanging down in the middle of the rotation. . I need to calculate the difference in tension when the bob is hanging vertically and when the chair is rotating. The length of the bob and string is 65.3 cm. The radius of the...
  32. J

    Reference that explains general relativity

    Hi guys, I need to write few paragraphs to explain Einstein's formulation of gravity in terms of the metric, christofell symbols, and Reimann curvature tensor. I also want to write about the veirbein and spin connection formalism of gravity. Can anyone suggest good, yet simple references...
  33. A

    Why is the speed of light same in all reference frames?

    kindly be descriptive
  34. A

    Events in different reference frames

    I am having trouble with measuring coordinate time in different inertial reference frames. For example: Say a car is driving around a circular track (at constant v) and passes a stationary observer. I'll call this event A. Then the car makes another lap and passes the observer again (Event...
  35. H

    Electrostatics and reference frame

    Hi, I'm stuck with a question concerning electric fields : Can an electrostatic potential drop exist in (what I would call) a 0 dimensional system ? Let's imagine we are in a region of space where there is nothing but a uniform magnetic field. So the problem is anisotropic but does not...
  36. J

    Major difference of Inertial and non-inertial frame of reference ?

    Major difference of Inertial and non-inertial frame of reference ?? What is the major difference or differences of Inertial and non-Inertial frame of reference?? Is it only: Inertial - Constant velocity, obeys the law of inertia Non-inertial - Acceleration, disobeys the law of inertia
  37. P

    Physics Reference Handbook: A Comprehensive Guide for All Levels of Study

    Hy! Might someone recommend a good physics reference handbook. It seem there's plenty of mathemathical ones around, but when it comes to physics, there are only books for certain areas. I've just started my 1. year of physics, and would laike to have a reference manual which i could use...
  38. 1

    Light's constant speed and frames of reference

    Been reading up on physics out of pure interest, just learning really. Mainly started special relativity and learning about the inertial frames of reference. I think I understand that, but here's what I don't get. If from one inertial frame of reference moving at a constant 100 MPH, I toss...
  39. M

    How to use results from different classes into one class by reference?

    Homework Statement I have: - 1 class to read a data series (see text file attached) (series.h and series.cpp) - 1 class for a function (function.h and function.cpp) I'm trying to create another class which has input from 2 above class (as constant references) and produce output which has...
  40. J

    Rotating Frames of Reference question.

    Homework Statement You are standing on a slowly rotating merry-go-round, turning counterclockwise as viewed from above. You are holding a string from which is suspended a rubber stopper of mass 45g. You are 2.9m from the center of the merry-go-round. You take 4.1s to complete one revolution...
  41. E

    Which reference should I choose for my DoD scholarship/internship application?

    Hey all, I'm applying for an scholarship/internship with the DoD at an air force facility. I have to submit two reference letters. One will be acadamic and I have that figured out. The second will be from one of two supervisors at my workplace where I am currently a co-op. The logical choice...
  42. J

    Different frames of reference and particle production? a contradiction maybe?

    Hi, Second time I'm writing this question, the first one seems to have been lost in cyberspace but sorry if it somehow comes back and appears twice. Anyway, you know how kinetic energy depends on velocity, so that the energy of a particle collision will be different for two frames of...
  43. B

    Problem in inertial reference frame

    Well, in principle, this problem seems very easy but I don't know the exact explanation.Here we go. We have a truck and a pack in its back.The bed of the truck is frictionless and the pack is stopped by a small piece of wood of something like that. The size of the pack is whatever(for...
  44. L

    Simple question about inertial frames of reference

    Hello, I know that this is going to sound stupid, so please forgive me, but could someone give me a brief and simple definition of what an inertial frame of reference is and what a non-inertial frame of reference is? Thanks, Louis
  45. D

    Reference suggestions for a struggling chemist.

    Hello All, Can anyone suggest some good references or books that can help me get used to working problems with the Dirac notation and the mathematics of Hilbert Space? I'm a new Ph.D. student in chemical physics, and I did my undergrad in Chem, with a math minor. I'm now taking graduate qm from...
  46. bcrowell

    Defining a manifold without reference to the reals

    Most definitions I've seen for a manifold are based on the idea that small neighborhoods are homeomorphic to \mathbb{R}^n. To me this feels a little like defining a bicycle as a car that's missing the engine and both the wheels on one side. The real number system is this big, sophisticated piece...
  47. Y

    Absolute motion's point of reference

    According to special relativity acceleration is an absolute motion, so according to what is it moving?
  48. K

    Find drag given reference area and speed

    Homework Statement What is the drag force on a 1.6 m wide, 1.4 m high car traveling at 30 m/s (approx 65 mph)? Homework Equations drag force=.5*p*v^2*coefficient of drag*A The Attempt at a Solution density of air depends on temp but that's not given so I used a density of 1.2...
  49. W

    Particle energy and momentum in different reference frames

    Homework Statement A particle is observed in a certain reference frame (i.e. observer A) has a total energy of 5GeV and a momentum of 3GeV/c. (a) What is the energy of the frame in which its momentum is equal to 4GeV/c. Homework Equations E'={\gamma}E-{\gamma}{\beta}(cp)...
  50. S

    Frame of Reference: Does Stuff in the Frame Matter?

    Okay, weird question. Sorry if this is really stupid but it's been bugging at me for days now. First, let me lay out my current assumptions/understanding of what's going on. The current theory seems to be (to an amateur like myself) that there is no fixed space-time. That to talk about...
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