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. A

    What is the Reference Frame for Rotational Motion?

    we generally study the concept of Inertial reference frame in case of translation motion (for non-accelerated frames) what happen if motion is rotational?
  2. A

    Inertial reference frame for 2&3 law

    Does the concept of Inertial reference frame also applicable for 2nd & 3rd law of motion?
  3. J

    Why no privlidged reference frame?

    I'm not a physicist and not a mathematician. I just want to understand things, and have read "advanced layman" books. It's often touted that Noether's theorem shows that the uniformity of space (the same everywhere; no preferred origin) implies conservation of momentum. More properly, the...
  4. Borek

    LaTeX LatEx reference in protected area of PF?

    I tried to check Tex reference when posting - I clicked already existing LaTeX image, clicked "LaTeX code reference" link - and I was aksed to enter user name and password to access protected area :bugeye: Seems like file https://www.physicsforums.com/misc/howtolatex.pdf is protected now for...
  5. K

    Why Is an Accelerated Frame of Reference Non-Inertial?

    Why an accelerated frame of reference is non-inertial?
  6. A

    Energy discrepencies depending on frame of reference

    The other day, I was arguing that a car traveling 70mph rear-ending a car traveling 55mph is the same as a car traveling 15mph rear-ending a stationary car. My argument was that, from the frame of reference of the car that was traveling 55mph, the energy of the other car is k(152), where k =...
  7. J

    Lorentz transformations ( synchronising reference frames?)

    Lorentz transformations ("synchronising" reference frames?) Homework Statement A particle moves from (x,y,z,t) = (0 m,0 m,0 m,0 s) to (1 m,1 m,0 m,10 ns). i. What is the speed of the particle in this reference frame? ii. What is the speed of the particle in a reference frame moving...
  8. jaketodd

    Relativity of simultaneity implies a universe for each reference frame?

    The fact that the relativity of simultaneity causes events to not happen at the same time, dependent on reference frame, seems to imply a separate universe or world for each and every thing in the universe. Different events at different times due to the relativity of simultaneity would lead to...
  9. K

    C according to what reference frame?

    This question may be nonsensical, but I have to ask. I'm a noob to relativity so please bear with me. All observers measure the same speed of light, correct? We also know that there is no favored frame of reference. So... what is to stop an object from accelerating to 0.95c, taking a...
  10. P

    Light speed in a non Inertial frame of reference

    Does the principle of invariant light speed still hold in a non Inertial frame of reference? Thank you!
  11. D

    Bullet vs Photon: speed of light, momentum and reference frames

    X________________ moving | observer | | ---> v (moving speed train) photon | ^________________| X________________ ^ moving | ^ ^ observer | d1 ^ ^...
  12. Grimble

    Time scales in Inertial Frames of Reference

    Hello, I am trying to understand the relationships of the time scales that obtain within different Inertial Frame of Reference. Not when viewing one frame from another, I am quite happy with the Lorentz factor for that. No it is how the local time scale, that measured by a stationary, local...
  13. C

    Is spacetime an absolute reference frame?

    STUPID QUESTION ALERT! Is spacetime an absolute reference frame?
  14. P

    P&ID Symbols Reference Textbook or similar

    To the viewer of this post, What is a good source for the symbols used in a P&ID? I would like to have a textbook or similar which would have all (if possible, or a majority) which I could easily reference to now and in the future when drawing/analysis P&ID's. Kind regards, pavadrin
  15. M

    Where Can I Find Helpful Engineering Reference Sites?

    Hello folks. I am looking to find reference sites which i can use them on my reports and assignments for mechanical engineering and to be helpful. Any help? Cheers
  16. D

    Velocity of rain in different reference frames

    I'm having some trouble with the below vector question. I've got an answer although I'm not sure if it is correct or not. Homework Statement A car travels due east with a speed of 40 kph. Rain drops are falling at a constant speed vertically with respect to Earth. The traces of the rain...
  17. F

    Newton 2nd law + frame of reference

    hello forum, i am struggling with the conceptual understanding of this problem: Given two blocks, one on top of the other. There is friction between the two blocks. The upper block is pulled with a force F. Thanks to friction, as long as F is smaller or equal to the static friction...
  18. T

    Reference book about astrophysics please

    hello, is there a book that give the proof about how to get the equations of time and the related topics like sun rise time and sun set time and other famous times (sorry i don't know the translation of it in english).
  19. G

    Linear Algebra Reference and Text

    Hello All I have recently recovered from a 4 year hospitalization which pretty much ended my career as a computer scientist. Much of the time I was barley lucid and thus time and medication have taken their toll on my memory. Although I retain much of the theory, I have found my knowledge of...
  20. P

    What would happen to an object falling towards a black hole?

    Hi Guys, I have a problem visualising a free falling object to use as a use as a theoretical reference body. I assume that a geodesic path would be the path that such a body would follow, but surely rotational dynamics would preclude such a situation. If there were theoretically such a body...
  21. DARKSYDE

    What is the smallest reference of time

    ive heard of nano seconds, pico seconds and what not, but I am wondering what the absolute resolution of time is? I am leaning towards infinite
  22. D

    Can Diodes or JFETs Serve as Effective Voltage References?

    I am trying to find a 2.5V voltage reference, but the only part available in the library I HAVE to use is a 2.5V LDO regulator. I need to have the 2.5V reference supplied from a varying 10 to 16 V source. What are other methods besides a zener or band-gap reference device that I can design a...
  23. Sirsh

    Excel help (V look up and a IF which are a logical and a reference.)

    Hi, Wondering if anyone can help me with figuring out of if it's possible to make a function on excel with V lookup and IF, if you can pls post an example. Or give an example of using both of these functions in a algorithm to reference to cells on another page in excel within the function...
  24. S

    Earth is a inertial frame of reference

    hi all of u WHAT IS INERTIA? and Earth is a inertial frame of reference or non inertial frame of reference? tell me briefly.
  25. A

    Electric field with reference to voltage

    If E=-∇V, does it mean that negative voltage emits positive electric field, and positive v negative ef?
  26. M

    Is there a reference of naturally occuring electromagnetic waves?

    I am interested in naturally occurring electromagnetic waves, is there a reference that lists wavelength, frequency, electric and magnetic fields, etc.?
  27. J

    How does the holographic principle relate to the reference frame of a photon?

    So if I'm a fast object moving in a sphere, in my frame of reference the sphere begins to contract along the direction I'm moving. As I approach the speed of light, the sphere begins to deform into a disk. If I'm a photon, the sphere is a disk. Rather than requiring requiring 4 coordinates to...
  28. C

    What are some good reference books to complement Calculus and Vectors course?

    What are some good reference books to complement "Calculus and Vectors" course? I am looking for a good book to help with Grade 12 Calculus and Vectors (MCV4U (ontario)). I am looking for good explanations and clear diagrams. Thanks.
  29. U

    Can objects move faster than the speed of light in certain reference frames?

    Here's a question that's bothered me for a while. Suppose you are a person (P) at point A. You travel between point A and B at some fraction of c (speed of light). And so relativity kicks in. Now, that's the standard relativity model and we talk about P with regard to A and B. Now, what...
  30. K

    Earth as a reference for electric potential

    If we apply the formula for the capacitance of a sphere (C= 4PEr, where P=pi, E= permittivity of free space, and R= radius of the earth), and apply the values we get a value of around 700 microfarad. If we now work out the potential on the surface of the Earth (V=q/c) we get a fairly high value...
  31. Y

    Telling if a reference frame is moving or at rest

    As stated in SR and the principle of equivalence, there is no privileged reference frame or reference frame at absolute rest. However, I went across the following idea that seems to be able to tell if a reference frame is moving or at rest. Please help me point out what is wrong in my idea...
  32. P

    Kinetic Energy of Objects in System, in different frames of reference.

    Hey! So, as I understand, kinetic energy of a moving object is proportional to its velocity squared. So I'm wondering where these inconsistencies come from, and how they are resolved: So, say two objects of mass M are travelling, with reference to a stationary observer, one in the left...
  33. Z

    How does the principle of Reference Frames work?

    How does the principle of "Reference Frames" work? What would be an appropriate answer for that statement? I can't think of anything fitting, also I'm not too educated in that subject. Any help is greatly appreciated. :)
  34. Z

    Frames of Reference on Top of a Moving Train

    When an object is thrown by someone standing on top of a moving train, which variations of "frames of reference" would apply? (i.e. inertial, non-inertial, etc.) How would this principle work? (The object would go the same relative distance as it would if thrown from a person standing on...
  35. B

    Changing the inertial reference frame to follow a mass in a collision

    Homework Statement We could change to inertial reference frame in a collision to follow a mass. But what would the down side be if we did? Homework Equations Vf1=(M1-M2)/(M1+M2)*Vi1 +2M2/(M1+M2)*Vi2 Vf2=2M1/(M1+M2)*Vi1 +(M1-M2)/(M1+M2)*Vi2 The Attempt at a Solution This question...
  36. K

    Time dilation and non inertial reference frames.

    Homework Statement A clock chimes every hour, on the hour in it's rest frame, is it possible for an observer to measure the time between chimes less than an hour? Homework Equations t = \gamma t0 The Attempt at a Solution I understand that if an observer traveling in the frame S'...
  37. B

    Reference Material for Electromagnetics

    I am in the final year of an MEng in mechanical engineering, working on my Final Year Project. I've been designing a solenoid actuated valve for a fluid power R&D outfit, so obviously a significant section of my report will be dedicated to electromagnetics. The mechanical engineers at the...
  38. S

    Is Self Reference Tied to Symmetry in Physics?

    Is there self reference in Nature? Foundations of The Quantum Logic
  39. I

    Communicating Vessels in a noninertial reference frame

    Hello all, Should be a simple question (just started Physics 1 not long ago). Here it is: The thin, fluid filled glass tube is sitting on an accelerating cart. As a result the level of the fluid rises as shown in the picture (attached) by D = 0.6 m. The distance L is given. L = 0.2 m...
  40. R

    Where Does Aristotle Discuss Objects in Motion?

    Oh the joys of the internet. I read everywhere that Aristotle felt that an object in motion would come to rest without any force acting on it yet no one wants to source anything. I can't find this in his writings myself though I do believe its there somewhere as it seems to be a commonly...
  41. fluidistic

    Confused about charged rotating disk-Magnetism, reference frame

    For some reason I've thought about the following case : A uniformly non conductor charged disk is rotating with an angular velocity \vec \omega. If I see it in front of me I'd observe a magnetic field since moving charges produce a current which produce a magnetic field according to Ampere's...
  42. R

    Inertial Frame of Reference & Equilibrium

    Is it safe to say that any object in an inertial reference frame is at a state of equilibrium? If so.. is it safe to say the opposite: that any object in a state of equilibrium is in an inertial reference frame?
  43. LarryS

    Can the SR Concept of Reference Frames be Applied to Quantum Mechanics?

    SR "Reference Frames" in QM ? The SR concept of “Reference Frame” cannot be transferred to the micro-world of QM because, due to the HUP, space and time are blurry in that world. Comments? (Thanks in advance).
  44. M

    Dealing with reference voltages and Vdroop

    My friend and I are building a telemetry system for a baja car to measure transmission temperature, fuel level, RPM, etc. that would include a wireless module for realtime monitoring as well as an SD card for backup, all powered from (probably) three 1.2V NiCd AA batteries in series with a...
  45. R

    How do you reference simultaneous publications to each other ?

    If i have three or four papers pending publication, review, rejection to another journal etc (a process out my control) and these papers depend on each other for clarification then how do you reference them to each other ? can you reference to a pending publication such as a repository held...
  46. M

    Defining a Lagrangian in an rotating reference frame frame

    Hi I'm trying to define a Newtonian lagrangian in an rotating reference frame (with no potential) Something to note is that the time derivative of in a rotating reference frame must be corrected for by: \frac{d {\bf B}}{dt} \rightarrow \frac{d {\bf B}}{dt} + {\bf \omega} \times {\bf...
  47. G

    What is the Centrifugal Force in Relation to Inertial Frames?

    I am confuse of what is inertial frame of reference. Can someone explain that to me? I need a clear explanation starting from the beginning to the end, and if possible, give me some set of example.
  48. A

    Classical mechanics reference book

    Hi All, Kindly suggest me an alternative book for "Classical Mechanics by Goldstein". I am finding it little bit difficult to understand so if i can find any alternate book which is little less complicated than Goldstein it will be helpful for me. I am concentrating on the below mentioned...
  49. D

    Understanding Time: Special Relativity & Earth's Reference Frame

    What does Special Relativity imply about past, present, and future time? So, here on earth, what can be said about our understanding of past, present, and future actions? Within the same reference frame, is time static? Is it ordered?
  50. S

    How to derive the ficticious force due to a moving frame of reference?

    Hi guys, I was reading the derivation of ficticious force due to moving frame of reference however i don't understand how they did it.There wasn't detail explanation for slow learners like me so i was wondering does anyone know where i can read up on this or give me some clue where i can start...
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