What is Frame of reference: Definition and 203 Discussions

In physics, a frame of reference (or reference frame) consists of an abstract coordinate system and the set of physical reference points that uniquely fix (locate and orient) the coordinate system and standardize measurements within that frame.
For n dimensions, n + 1 reference points are sufficient to fully define a reference frame. Using rectangular (Cartesian) coordinates, a reference frame may be defined with a reference point at the origin and a reference point at one unit distance along each of the n coordinate axes.
In Einsteinian relativity, reference frames are used to specify the relationship between a moving observer and the phenomenon or phenomena under observation. In this context, the phrase often becomes "observational frame of reference" (or "observational reference frame"), which implies that the observer is at rest in the frame, although not necessarily located at its origin. A relativistic reference frame includes (or implies) the coordinate time, which does not equate across different frames moving relatively to each other. The situation thus differs from Galilean relativity, where all possible coordinate times are essentially equivalent.

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  1. X

    Relativistic speeds within a relativistic frame of reference

    Astronauts on a long space journey are playing golf inside their spaceship, which is traveling away from the Earth with speed 0.6c. One of the astronauts hits a drive exactly along the length of the spaceship (in its direction of travel) at speed 0.1c in the frame of the spaceship. What is the...
  2. M

    Velocity of light and it's frame of reference.

    If light has a maximum speed of c, what frame of reference is that speed determined from? For example, if you were to turn on a light bulb moving at a constant rate and measured when the light in every direction got to one light year away from it's source, wouldn't some of it reach that...
  3. M

    Inertial Frame of Reference: Why Space Selects a Non-Inertial Frame

    Why does one particular 'frame of reference' have fictitious forces (like inertia) whilst another one doesn't. I understand the basics, but more interested in 'why' space seems to have magically chosen specific frame to be the 'non inertial frame'. Could space be more absolute than we...
  4. L

    How would you define an inertial frame of reference?

    I've researched about it and watched a few videos, but I can't seem to get my head around it. Would saying that "it's a marker that is fixed relative to your position, in which Newton's first law holds" be an accurate way to define it?
  5. 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...
  6. 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...
  7. 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...
  8. 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...
  9. R

    Where is the intertial frame of reference applicable?

    (Please forgive me for the obvious stupidity of this question) I'm trying to understand Newton's laws down to the last detail, because that is how I study things. However, where would the principle of inertia ever take place? And since Newton's laws are only applicable in an inertia frame...
  10. I

    Frame of reference - forces in a turn (airplane)

    Hi, I've seen the forces in a turn depicted two different ways: http://selair.selkirk.ca/Training/Aerodynamics/images/lf-turn.gif http://www.free-online-private-pilot-ground-school.com/images/forces_during_turn.gif Which one is correct? I think the first one would be since it's...
  11. X

    Physics frame of reference, is this possible?

    Homework Statement Generic collision question. For example, let's say you are asked the following question: Object 1 is 10kg and is traveling at 10 m/s [right] Object 2 is 5kg and is traveling at 2 m/s [right] Find their final collisions after impact Homework Equations m1v1 +...
  12. O

    Can an Electron Be a Frame of Reference in Quantum Mechanics?

    How does the concept of frame of reference apply to quantum mechanics? Classically something can be a frame of reference as long as it is not accelerating. I often picture in my head an atom with the nucleus fixed and the electron cloud surrounding it. Would it be possible to describe an atom...
  13. A

    Changing the Hamiltonian to a new frame of reference

    Suppose I'm considering particles of mass \mu_i, 1 \leq i \leq 3, located at positions r_i. Suppose I ignore the potential between \mu_1 and \mu_2. Then the Hamiltonian I'd write down would be H = -\frac{1}{2\mu_1}\Delta_1 -\frac{1}{2\mu_2}\Delta_2 - \frac{1}{2\mu_3}\Delta_3 + V_1(r_3 -...
  14. W

    Change frame of reference to simplify acceleration calculation?

    I'm working problem from the upper division classical mechanics course on MIT OCW. No solutions are available. This is form the first P-set, question 4. Homework Statement A particle moves in a two dimensional orbit defined by x = A(2αt-sin(αt)) y = A(1-cos(αt)) Find the tangential...
  15. E

    No privileged frame of reference

    As I understand it, Einstein's dismissal of the "luminiferous aether" was based on his discovery that there is no universal frame of reference, i.e. that no frame of reference is privileged in relation to all other frames. My question is whether this principle can also be stated in the inverse...
  16. B

    Frame of reference question about equivalence principle

    I've been giving some thought to the new scientist article about the equivalence principle. What initially seems like a very simple issue is remarkably tantalising. (please note- I'm not a physicist so this may be quite stupid) This led me on a little to the question of gravity and direction...
  17. T

    Does light have a frame of reference?

    I know that you're going to probably say that a frame of reference doesn't make sense for light, but I've uploaded a discussion (warning: has profanity) from another website (reddit.com) and I'm curious to see if the user Imhtpsnvsbl makes a valid point.
  18. D

    Can Something Travel Faster Than Light in Different Frames of Reference?

    hello, in relativity something can go faster than the speed of light as long as it is not in the observer's frame of reference which would say that a FOR has a size but i read that a FOR was infinite in all directions. Someone explain this contradiction please!
  19. A

    Change of Schrodinger equation when we change frame of reference

    Hi! I think this should be a fairly easy question to resolve, but it's currently giving me fits... Suppose we consider a system of three interacting particles where we assume two of the particle (at positions r1 and r2) have infinite mass (such that we can ignore their kinetic energy) and do...
  20. S

    Cause and Effect Without Frame of Reference

    Before I say anything, I don't really have any experience in physics. But this question just popped into my mind concerning cause and effect and I can't seem to find the answer to it on the web. Here it is...Are cause and effect the same thing if a frame of reference is not present? For...
  21. Chestermiller

    Definition of Frame of Reference

    In studying SR, I've been subscribing to a particular definition of a Frame of Reference that makes sense to me. Recently, I've been made aware by another PF member that there may be other, broader, definitions that are valid and that people use. I would like to know more about these broader...
  22. S

    Observer Frame of Reference

    Practicing Lorentz transformations but still not absolutely clear about conditions for observer's frame of reference. For example: Suppose that just as one of Einstein's long and surreally fast trains is passing a station platform, lightning strikes the platform at two points making scorch...
  23. S

    Problem on frame of reference in rotation

    Homework Statement I wanted to know if I consider the frame of reference as a rotating body itself, then will the points lying on the body rotating be stationary with respect to the rotating frame of reference? Homework Equations None The Attempt at a Solution As per me, if I am...
  24. P

    Frame of reference for Fermi Golden Rule

    Hi guys. I am currently studying Sub-atomic physics and it seems to me that there are different formulas that work in different frame of reference. In particular, I would like to ask: 1. Which frame should we use in applying Fermi's Golden Rule? (I've read somewhere that the matrix element...
  25. bayan

    Frame of reference and relativity.

    Homework Statement You are flying your personal rocketcraft at 0.9c from Star A toward Star B. The distance between the stars, in the stars' reference frame, is 1.0 ly. Both stars happen to explode simultaneously in your reference frame at the instant you are exactly halfway between them...
  26. R

    Is there a frame of reference where events A and B are simultaneous?

    Hi there! I'm working on a couple of problems regarding simultaneity. For one I'm given events X_a = (ct,x,y,z) = (2,1,-3,2) and X_b = (6,3,-1,5) I want to find out if there's a frame of reference where the events are simultaneous. I find the change vector X_b - X_a = (Δct,Δx,Δy,Δz) =...
  27. T

    Conserved Energy in a moving frame of reference

    Homework Statement When the box is at the bottom of the incline it will have a velocity of vf The person is an inertial frame of reference with a velocity of vf When the person starts moving, the box is moving backwards with the velocity of vf. This means at the top of the hill the box has...
  28. A

    How inertial frame of reference differs from non-inertial frame?

    We know that we can't say whether we are at rest or uniformly moving if we're in a einstein cage..but if the same medium is accelerating/decelerating can we being inside(and can't see outside) claim abt state of cage..?I ve read that a non-inertial can be converted to inertial by incorporating a...
  29. zdcyclops

    Particle paths in relativity: frame of reference and double slit results

    The apparent path of an object is different for observers in different reference frames. A ball dropped from the top of the mast on a moving ship lands at the base of the mast. An observer on the ship sees the path as straight down while one on the dock sees the path as a diagonal. How many...
  30. sankalpmittal

    Clarifications regarding frame of reference.

    I have just completed my class 10th. I was presently reading the class 11th H.C Verma physics textbook and here is what I confronted which seems to me as if I am unable to fathom : Now I can't understand that how come acceleration of book with respect to Earth isn't 0 ?! Please see bold part...
  31. L

    Why should the speed of light be the same in every frame of reference.

    If we have light, any particle, and maybe car, the particles travel at 0.98c and car let say 50m/s. Let them start moving at the same time to the given point let say 300 metres away. The difference between times of arrival of light and particle will be small compared to that between light and...
  32. @

    This question is not about a moving clock, but about the frame of reference.

    I found out that Proxima Centauri is 4.2 light years away from earth. If someone was on a voyage to this star via space ship, would this person measure the time to be shorter than 4.2 years if their spaceship was traveling 99.99999 percent the speed of light, assuming that the 4.2 years is...
  33. E

    Inertial frame of reference of light speed (And beyond)

    Hi All! I found discussions on this here while researching the subject to see if anyone else has attempted to explore the subject. I saw that several people asked questions pertaining to this, but the question was never really answered. It seemed unanswerable. While many discussions of...
  34. 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...
  35. 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...
  36. 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...
  37. 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...
  38. 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?
  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. 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...
  41. 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...
  42. 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...
  43. 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...
  44. 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...
  45. 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...
  46. 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...
  47. 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...
  48. 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...
  49. 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
  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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