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. J

    Intuitive understanding of the reference solution (numerical analysis)

    Hello I am having some trouble understanding what the difference is between the reference solution and the "true" solution of a set of certain differential equation. The book I'm working with is Numerical Analysis by Walter Gautschi. Equation 5.16 from this book is a set of first order...
  2. P

    Lift and Drag Which frame of reference?

    Lift and Drag...Which frame of reference? Hi, When expressing the Lift and Drag acting on an airplane as: F_{lift}=qSC_L F_{drag}=qSC_D where q is the dynamic pressure, S is the wing ref. area, and C's are the lift and drag coefficient. My question: Some sources, like this one...
  3. M

    Defining Reference Entropy and Chemical Potential in Different Phases

    Supposing that some solid can exist at 2 different phases (had 2 different crystalline structure) at some temperature and pressure. Can we define the same reference entropy or chemical potential for these two states (knowing that we are talking about the same solid)?
  4. C

    Mass of MW within 8.5kpc: Refs for Simon

    Hi all, For my second year project at university, I have collected and analysed 21cm data of the Milky Way (MW). I have created a rotation curve, estimates of the mass and mapped the spiral arms in quadrant 1. I am having trouble finding a paper to compare my work to, I especially need one...
  5. mrnike992

    Could there be an absolute 'state of reference?'

    Could there be an absolute 'state of reference' somewhere in the universe, perhaps at the location of the original center? If so, would it have to hold the same frame of reference in each dimension, including time? How would it do so? Looking at the Hafele-Keating Experiment in particular...
  6. Shackleford

    Graduate Reference: Getting a Professional Math Ref.

    I've finally decided to start the M.A. Math program at my university. It's designed for those who want to teach math at a junior college, but I have no plans to do except maybe for "retirement" later in life. It's not a science/research degree, but I want to learn more mathematics, primarily the...
  7. M

    What is a Standard State or Reference State of an element?

    What is a Standard State or Reference State of an element? Can someone please give me a simple explanation of what a standard state or reference state is? I don't quite understand the way wiki describes it which is - The standard state, also known as reference state, of an element is...
  8. C

    Continue work with reference to Thread # 304738

    I have gathered experimental data regarding this heat transfer problem. Unfortunately right now there is no simple way to measure discharge water temperature. On the theoretical approach developed on post # 10 of abovementioned thread, a water temperature increase of 50 °C was considered...
  9. S

    Collisions, Impulse, and Reference Frames

    A racquet ball with mass m = 0.245 kg is moving toward the wall at v = 15.4 m/s and at an angle of θ = 28° with respect to the horizontal. The ball makes a perfectly elastic collision with the solid, frictionless wall and rebounds at the same angle with respect to the horizontal. The ball is in...
  10. P

    Voltage of an infinite cylinder with nontrivial reference point

    Homework Statement Find V(r), the electric potential due to an infinitely long cylinder with uniform charge density ρ and radius R. Use V(r = 2R) = 0 as your reference point. Homework Equations E at r < R = ##\frac{(ρr)}{2ε_{0}}## E at r > R = ##\frac{(ρR^{2})}{(2ε_{0}r)}## The...
  11. D

    SR830 Lock In Amplifier Not Reading Reference Signal

    So here is my dilemma: We have our SR830 in a MOKE set-up. The modulation of the laser is with a chopper at approximataly 336 Hz. The reference signal is not being picked up by the SR830, but using the same cable the reference frequency is coming up on our oscilloscope. ie, plug the cable...
  12. wheelersbit

    What causes a collapse - and does it depend on frames of reference?

    I know there are many wavefunction collapse models - but with regards to the Copenhagen interpretation the idea is that a measurement will cause something to collapse into a particular state. What does the term "measurement" refer to? It makes one think of only something that a conscious being...
  13. .Scott

    Coarsening the reference vs. the detection?

    According to phys.org: This is very unclear to me. How would one coarsen a reference angle? It seems to me it would be very difficult to set an angle without being able to check it later to determine exactly what angle you ended up setting. On the other hand, coarsening the detection...
  14. F

    Reference for N=4 d=3 SuperYangMills

    Hi! I am looking for a review article on extended N=4 supersymmetry in 3=2+1 spacetime dimensions. (8 supercharges in total). I am familiar with the N=1, d=4 case, but now I need to study the N=4, d=3. Is anyone aware of the existence of such an introductory article, or a book in which this...
  15. S

    Looking for reference on decay randomness

    Hello, Sometime in the last 6 months I read that researchers analyzing data from the decay of a subatomic particle and reported that the decay appeared to be random or unpredictable. I recall they said this particular reaction was very low level. This would have been in either Science, Nature...
  16. dextercioby

    Where Is the Two-Loop Correction to g?

    Dear all, please, see this wiki page: http://en.wikipedia.org/wiki/Anomalous_magnetic_dipole_moment Am I missing something obvious, but I can't find a reference to the two-loop correction (a term ~ alpha2) to g :( Where can I find it ? Thanks!
  17. G

    Discussion regarding the frames of reference

    A person is inside a car. This person is not using the seat belt. The car crashes with a solid wall and decelerates quickly. The person, due to inertia, keeps moving until stopped by the wind shield. I want to analyze the movement of this person after the crash, but I am troubled...
  18. D

    Frame of reference in a simple harmonic motion vertical spring

    I have doubts of how can I put my frame of reference in a simple harmonic motion vertical spring. Normally the books choose the origin in the equilibrium position and the positive distance (x>0) downward, and in this conditions Newton´s second law is: ma=-kx; but instead of putting the positive...
  19. B

    Time Lapses In Two Different Reference Frames

    Hello, I would like to prove that the time experienced in a moving reference frame is longer than in a stationary frame. Here is my solution: Suppose that at time t = 0 two reference frames, S and S', origins coincide; similarly, the x,y, and z axes of the S-frame overlap with the...
  20. F

    Change in kinetic energy between reference frames

    I was trying to do some studying regarding the definitions of energy, and I've hit a road block. I know that since velocity is frame-dependent, an object's kinetic energy as observed in two different frames will yield two different results. My initial expectation was that changes in...
  21. M

    Basic non-rotating accelerating reference frame problem

    Homework Statement A uniform thin rod of length ##L## and mass ##M## is pivoted at one end. The pivot is attached to the top of a car accelerating at rate ##A##. What is the equilibrium value of the angle ##\theta## between the rod and the top of the car? Homework Equations None in...
  22. T

    What is {001} in reference to the surface of TiO2?

    Homework Statement I am an EE in a research group and we are required to read up on some articles for the project. My chemistry knowledge is not the best so I need some assistance understanding some terminology. The article references the {001} surface of anatase TiO2. Can someone explain...
  23. PeroK

    Simultaneity between events in reference frames

    Hi, I've been trying to understand the (lack of) simultaneity between events in reference frames moving wrt each other. I'd be grateful if someone could confirm that I've got things right: If two events are simultaneous in one reference frame (S'), then they will not be simultaneous in a...
  24. E

    Concept of coordinate reference frame in GR

    In SR there is a whole family of so called inertial observers that are defined as those observers that move at relative constant speed with respect to one another, whose descriptions of nature are all equivalent and whose spacetime coordinate are related by Lorentz transformations i.e. those...
  25. C

    [C] Lab question. (Pass by reference)

    a)Write a function,named getNumSum(),for accumulating(summing)float numbers; -The function has no return value -The function has 1 input argument named aSum:the current accumulative sum to be "updated" inside this function(Hint:use pass by reference) -The function asks user for a float...
  26. H

    Rotating reference frames and acceleration

    My question stems from a conversation I had recently with another physics buddy of mine and has to do with rotating reference frames and acceleration. Say, in a non-rotating reference frame you have an object with a known position. For the sake of argument, say it has a position A of 0i + 2j +...
  27. R

    Theoretical MFI Values of Common Polymeric Materials Reference

    Where can i get the theoretical value of MFI for common polymeric materials such as PP, PE, PS, PMMA...as reference?
  28. H

    Reference Electrostatic Potential

    What is the criteria in choosing infinity as zero potential ? e.g. an infinite plate with uniform charge density. What is the physical meaning of not be able to choose a position as reference potential ??
  29. H

    DC Generator Reference Books for Aeronautical Engineering Students

    I have completed a DC generator chapter from my course book. Below mentioned questions have been asked in previous examinations, but my course book doesn't help in solving these. Please help me with the reference books which will be helpful in solving these type of questions. I am pursuing...
  30. S

    Measuring an angle in non-inertial frame reference

    In class, we came up with an equation, a=gtanθ, to calculate the acceleration of a car using a hanging pendulum in Earth's frame of reference (θ being the angle that the pendulum makes with the vertical when the car accelerates). So far, I know that that the pendulum moves in the opposite...
  31. D

    Understanding non-inertial reference frames in CM and SR.

    Sorry if this is a frequent topic, but I think it's interesting and probably worth repeating if it's come up often before. Let me lay out my question by example (and if anything is inaccurate feel free to point it out), and then I'll summarize at the end. It's easy to show in Classical...
  32. J

    Causality and FLT a time reference consideration

    excuse my lack of understanding! Is there anything in physics which directly suggests that if FLT was possible, you would travel back in time? does anything forbid the possibility that instead you gradually change your time reference to keep causality? With the example of a very fast train, a...
  33. A

    Kinetic Energy in Reference Frames

    K'sys=1/2MtotalVcm2+1/2\muVreli2 I understand this equation represents the total kinetic energy in a reference frame. What I'm not getting out of this is the overall concept. I understand that the first part of the equation is supposed to represent the total kinetic energy required to...
  34. W

    Electrochemistry Reference Electrodes

    Homework Statement Change your electric potential readings from a Ag/AgCl system to a RHE (reversible hydrogen electrode) system at pH 7. For example, 0.3 V vs Ag/AgCl and -0.1 V vs Ag/AgCl Homework Equations Ag/AgCl 0.222 Volts RHE 0 - 0.0591*pH Volts The...
  35. M

    Doubt in Inertial frame of reference

    Newton's laws of motions are not applicable in Non-inertial frames of reference which means only mutually accelerated frames of references, My question is how can we apply Newton's laws of motions for practical experiments such as simple pendulum, motion of a ball, etc. conducted in near surface...
  36. M

    Reference frame in relative motion

    I red a classical mechanics concept in a book. Imagine that we have two observers with two frames of reference F1 and F2 observing a particle P in motion. One of the observer is in motion and another is at rest,(lets take F1 is at rest and F2 is in translation motion with velocity V) let r1 be...
  37. WannabeNewton

    Proper Reference Frame -Accelerated observer

    "Proper Reference Frame"-Accelerated observer Hi guys. This is regarding section 13.6 (p.327) in MTW. Here the authors consider an arbitrary accelerated observer in any space-time and construct a set of local coordinates carried along the entire worldline of the oberver with the origin of the...
  38. Hyo X

    Where Can I Find a Comprehensive Reference for Bond Strengths?

    Hi, I am looking for a good reference on the relative strengths of several bonds. (I think this is the same as bond dissociation energy?) I.E., C-C, C-S, C-N, S-Au, etc. Is there a good reference out there? thanks
  39. K

    Primary reference paper for presentation

    Hi all! I am a first year BS-MS student and I need to make a presentation on a paper or a review article from a primary reference journal. The broad topic is particle physics. I searched on Physical Review D, Nature and Science but couldn't get anything which was not too mathematical...
  40. D

    Common Reference OSC for test equipment

    Can someone please explain to me what if any is the benefit in using one lab quality 10 MHz OSC to run all your bench equipment ref OSC inputs? And, what about this GPS thing? Why use an expensive GPS synced 10 Mhz OSC source to drive your test bench? Thanks
  41. V

    Choice of reference potential in electrostatics

    Homework Statement While solving problems in electrostatics we assign zero of potential to infinity .But we also assign zero to ground as well. Now there are electrostatics problems where we use both ground and infinity as zero potential .How is that we have two zero potentials within a same...
  42. D

    DQ Reference Frame in VSC Station: Fig. 1(b)

    Each VSC station has the same configuration, and its vectorbased equivalent circuit in the synchronous dq reference frame is shown in Fig. 1(b). Could someone please explain me what doe "dq reference frame" mean?
  43. Q

    Time Effects in Separate Frames of Ref.

    Hi, before I question let me say I'm new both to this site and Physics in general, as such please forgive any ignorance on my part. I was given an example of time difference in regards to a 'my twin traveling at near the speed of light' scenario and I'm having trouble reconciling some of the...
  44. A

    Inertial reference frames in general relativity

    Hi guys, I was reading some stuff about general relativity and the first impression is that isn't completely the follow-up to SR. In what I've read it has a different assumption about inertial frames, that they are only significant only locally. What does this really mean and what are the...
  45. A

    Interchanging a position between two reference frames?

    \vec{r}_a is a positional vector from reference frame a. What is the position of same point from reference frame b ? If required, assume position of origin of frame a is \vec{m} and unit point (i.e. \langle 1,1,1\rangle_a ) is \vec{n} from reference frame b. I am studying Kleppner and Kolenkow...
  46. I

    Independency of the frame of reference of the strain rate tensor

    I've got a problem regarding tensors. Premise: we are considering a fluid particle with a velocity \mathbf{u} and a position vector \mathbf{x}; S_{ij} is the strain rate tensor, defined in this way: \displaystyle{S_{ij}=\frac{1}{2}\left(\frac{\partial u_i}{\partial x_j} +\frac{\partial...
  47. M

    Earth's Rotation and Frames of Reference

    I have a question about Earth's rotation around its own axis. Earth rotates at around 1000 miles per hour. However, if I stand in an open field and let a balloon float beside me in mid-air, I wouldn't expect the balloon to fall away (or appear to fly away) at that speed when I let go of it. I...
  48. S

    Use of a non-inertial reference frame in a problem involving rotation?

    Homework Statement A disk rotates with angular velocity ω. It has a groove cut along the diameter in which two blocks of mass m and M slide without friction. They are connected by a light string of length l, fixed by a catch with block m a distance r from the center (r + radius of M = l)...
  49. S

    Motion of Reference Frames wrt each other

    I am currently working on a Python script to simulate motion of reference frames wrt each other, and I need some help with the math. Here is the problem statement- Suppose I have a frame A A frame B frame B's origin has pos-vector PB,A (function of time) wrt A in frame A frame B is...
  50. D

    Reference frame for analyzing ball rolling down incline

    Hi all, I have a question about how to analyze the problem of a ball rolling down an incline plane. Assuming there is friction, at each instant the ball swivels about a pivot point on the incline that is stationary due to static friction. We then would analyze the torques about this point...
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