What is Reference frames: Definition and 227 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. C

    Accelerated reference frames equation derivation question

    my question comes from the portion of the derivation regarding evaluating the rate of change of the principle axis vectors. this begins by supposing a vector, Q, is rotating about axis n by δθ. Specifically, my question is how from step 4 to step 5 the approximation becomes an equality. Q'...
  2. C

    Accelerated reference frames equation derivation question

    My question regards how the approximation becomes an equality.
  3. S

    Special Relativity with Three reference frames

    Homework Statement In the laboratory frame, event 1 occurs at x = 0 light-years, t = 0 years. Event 2 occurs at x = 6 light-years, t = 10 years. In all rocket frames, event 1 also occurs at the position 0 light-years and the time 0 years. The y- and z- coordinates of both events are zero in...
  4. P

    Special Relativity, calculating velocity of Kl0 meson with reference frames

    Homework Statement K mesons (“kaons”) are unstable particles composed of a quark and an antiquark. They can be produced copiously in energetic collisions between stable particles at accelerator laboratories. Soon after they are produced, kaons decay to lighter particles. One type of kaon...
  5. B

    Relative Acceleration in Noninertial Reference Frames

    Homework Statement Suppose you have a spaceship and in the spaceship is a block on an frictionless incline. Initially, the spaceship is at rest on the Earth's surface. The astronaut in the spaceship observes the block sliding down the incline with acceleration Mgsinθ . Now consider that the...
  6. A

    Switching inertial reference frames equations

    What is an inertial reference frame?How are positions,velocities and accelerations changed when switching between different inertial reference frames? r=rx i + ry j + rz k Inertial reference frame:It is a frame of reference where Newton's laws of motion is valid.No fictitious...
  7. B

    Do different reference frames agree with total energy?

    I know total energy is conserved, but does this mean that different frames agree on the total energy of a particle? I'm assuming they don't agree on energy, because if I measured the total energy of a particle moving relative to me (which would equal the rest energy plus its kinetic energy)...
  8. S

    Lenght Contractions in Inertial Reference Frames

    can inertial reference frame ever have "lenght contractions" in 3d or in rest? hi! thank you for all answers in this topic in previous threatin same topic. i open this new thread in same topic but here i try to keep the issue here very short and readable , with no speculation and concentrating...
  9. B

    Lorentz Transformation/converting between reference frames

    Homework Statement Particle track detectors are used to measure the speed of particles if the lifetime of the particle is known. Particle X has a lifetime of 256.2 ps. These particles are created in an experiment inside the detector by a given reaction. The particles leave 21.8 cm long tracks...
  10. N

    Reference Frames? Putting multiple perspectives in kinamatics in 2D problems

    Homework Statement I have this assignment on where I have to make up a scenario and solve for the question. The question is that there is a baby that is being thrown out of building into a moving car, (to keep the baby out of harms way). How fast would the car have to traveling to catch...
  11. C

    Mass the same for two reference frames

    Homework Statement There are two particles with rest masses m1 and m2. In the S frame they have velocities u1 and u2. Consider another frame, which we usually denote as the S0 frame, which has a velocity v in the S frame in the direction of increasing x (i.e., it is going to the right in the...
  12. PhizKid

    I don't understand reference frames

    I've read all sorts of descriptions in textbooks and online, but I don't get the purpose of reference frames. Why can't you just put everything on the same set of coordinate planes? I don't see what difference it makes. There was an example with a car traveling alongside another car, and that to...
  13. K

    Moving Reference Frames: One Car Passing Another

    Homework Statement You are traveling in a car going at a constant speed of 100 km/hr down a long, straight highway. You pass another car going in the same direction which is traveling at a constant speed of 80 km/hr. As measured from your car’s reference frame this other car is traveling at...
  14. R

    Inertial/non-inertial reference frames

    I'm a bit unsure about the last couple of bits of this question, and I'm hoping someone might be able to help. Homework Statement a) Let a reference frame with origin O & Cartesian axes (x, y, z) be fixed relative to the surface of the rotating Earth at co-latitude θ (i.e. 0≤θ≤∏, where θ...
  15. S

    Understanding Inertial reference frames

    Hi to all, I am a new one to this physics forum and i have a doubt regarding Inertial Reference frames. In an article of IRF, it is given as "There is no absolute inertial reference frame, meaning that there is no state of velocity which is special in the universe." Can anybody please...
  16. 0

    Special relativity of space traveler and reference frames

    Homework Statement A space traveler takes off from Earth and moves at speed 0.99c toward star Vega, which is 26.00 ly distant. How much time will have elapsed by Earth clocks when the traveler reaches Vega? 2. The attempt at a solution I looked at the problem solution, which...
  17. Vorde

    Something I've never understood about non-inertial reference frames

    Basically: I jump forwards, exerting an amount of energy enough to push me forward with some velocity. But in my reference frame, I exert the same force, except the entire universe moves backwards with that same velocity, where did that energy come from? I sort of know this has to do with...
  18. L

    Confused about reference frames

    Ok I'm really trying to understand inertial and non-inertial reference frames, my understanding is as follows: A rest observer on the earth, the observer will be stationary relative to the earth.. Now as I understand it an inertial reference frame is one of which 2 coordinate systems are both...
  19. M

    How to trasform an orthonormal system in two reference frames

    My question is not homework. I feel ashamed of having this doubts but I'm really stuck on this. The problem is I have a reference frame xyz and here I define the COM \vec x{_{cm}} of the system. Now I move the COM reference frame x'y'z': \vec{x'}=\vec{x}-\vec x{_{cm}} In this reference frame I...
  20. M

    Velocites in Different Reference Frames

    Homework Statement The Millenia is catching up to the Galaxa at a rate of 0.55c when the captian of the Millenia decides its time to fire a missle. He uses a laser range finder to determine the distance to Galaxa and then he fires a missle that is moving at a speed of 0.45c. What...
  21. A

    Releativity and reference frames. Spaceship traveling faster than speed of light?

    Homework Statement The distance from Planet X to a nearby star is 12 Light-Years (a light year is the distance light travels in 1 year as measured in the rest frame of Planet X). (A) How fast must a spaceship travel from Planet X to the star in order to reach the star in 7 years...
  22. JimiJams

    One Dimensional Collision dealing with Reference Frames

    Homework Statement A 20g ball of clay is shot to the right at 12m/s toward a 40g ball of clay at rest. The two balls of clay collide and stick together. Call this reference frame S. Homework Equations What is the velocity of a reference frame S' in which the total momentum is zero...
  23. M

    Why do Newton's laws only apply in inertial reference frames?

    Hello, I am having difficulty understanding the concept of Newton's first law only applying in an inertial reference frame, or a frame that is at constant velocity, however, apparently the 1st law no longer applies if the reference frame is accelerating. Can anyone give me some sort of concrete...
  24. H

    Relativistic Rocket: Find Δv in Earth Frame

    Homework Statement I a little lost on how to use the relativistic velocity addition formula to determine the increase in speed "v" over a short time interval in the Earths frame of reference, for a rocket having left Earth at rest and traveling through space accelerating at constant acc. of...
  25. M

    Problems with Inertial Reference Frames

    The initial presentation of Newton’s Laws of Motion (NLM) to students often proceeds as follow: 1. The 3 laws are presented, 2. The caveat that the laws are only valid in Inertial Reference Frames (IRFs) is (sheepishly) mentioned, 3. An attempt is made to define an IRF, and 4. Some examples...
  26. J

    Light in local reference frames in extreme gravitational fields.

    As I understand in SR light is always c in it's local reference frame regardless of a present gravitational field. Light would appear to be traveling slightly less than c in a gravitational field otherwise known as the Sharpio Delay in all non-local reference frames. Now, light must be traveling...
  27. K

    Conceptual Question about reference frames

    Homework Statement Do objects same kinetic energy in all inertial reference frames? For objects interacting, is energy conserved in all inertial reference frames? Homework Equations None The Attempt at a Solution I think the answers are No for the first one, and Yes for the...
  28. J

    KE of system / different reference frames question

    I am re-posting this question here in a new thread as Humber mistakenly posted it in a two year old thread.
  29. N

    Existence according to reference frames

    Is it possible for a particle to exist according to one reference frame and simultaneously not exist according to another? If energy is relative, can a collision between two particles have enough energy to produce new particles according to its own reference frame but not have said amount of...
  30. T

    Difference Between Inertial & Non-Inertial Frames | Practice Numericals

    i came over the terms 'inertial' and 'non-inertial' frames during the study of rotational motion...pls clarify the difference...! plus can anyone give me a link from where i can practice numericals of angular momentum, moment of inertia, torque..
  31. S

    The speed of light, the term light year , and reference frames.

    The speed of light, the term "light year", and reference frames. Hi everyone. This is my first post, and I post out of desperation. A friend of mine and I were casually discussing Time Dilation, interstellar travel, etc. when we came to a point we fundamentally disagreed upon. Neither of us...
  32. T

    Inertial reference frames and Newton's Laws of Motion

    The first law of motion says that it takes force to accelerate something. The second law of motion says that F=ma. So now my teacher says that the first law is for inertial reference frames, while the second is for non-inertial reference frames. This really annoys me because I don't...
  33. E

    Simple question about time dilation in accelerated reference frames

    If one wants to calculate the elapsed time from the perspective of an object A moving at velocity, v, for time, t, relative to a stationary object B, all you have to do is calculate: \int_{t_o}^{t_f}\frac{t}{\gamma} Of course, \gamma has no dependence on t because v is constant, so we get...
  34. M

    Frame of Reference: Constant Velocity & Inertiality

    a frame of reference is moving with a constant velocity with respect to a inertial frame of reference,then moving frame will be inertial itself?
  35. J

    Torque (changing reference frames and adding)

    Hello there I have 2 questions: 1. Can one change the coordinate system of torque vectors through a homogeneous transformation matrix with both rotation and displacement? 2. What's the procedure to add two torque vectors about different axes? Thanks in advance, João
  36. J

    Are You an Inertial Observer on a Constantly Moving Turntable?

    An inertial frame is one which is not accelerating. i.e if I'm sitting in an accelerating bus or plane I'm not an inertial observer however if I am in a bus or train traveling at a constant velocity i.e zero acceleration then I am an inertial observer. One thing Id like to ask here is that...
  37. A

    Calculating Time Period for Simultaneous Relativity in All Ref Frames

    Homework Statement Challenge: a rather eccentric group of astronomy students wanted to celebrate the impact of the Shoemaker-Levy comet on Jupiter by holding a party of sufficiently long duration that their celebrations were simultaneous with the impact of the comet in all inertial reference...
  38. Y

    Two dimensional collision. Center of mass reference frames?

    Homework Statement [PLAIN]http://online.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?courses/phys211/oldexams/exam2/sp10/fig3.gif A 4.0 kg circular disk slides in the x-direction on a frictionless horizontal surface with a speed of 5.0 m/s. It collides with an identical disk that is...
  39. C

    Why is light speed constant in all reference frames?

    Hey, this is my first post. I am a biology major so I know pretty much nothing about physics, yet sometimes it interests me way more than chromosomes do. So, given that I know nothing about physics, this is probably going to sound like a stupid question. But I've always wondered how it is...
  40. R

    Comparing Sidereal & Synodic Reference Frames

    This website has an animation that shows the difference between sidereal reference frames and synodic. http://www.sumanasinc.com/webcontent/animations/content/sidereal.html The motion of the moon is circular about the earth, yet apparently the moon has an apogee length that is 50,000 km...
  41. 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...
  42. 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...
  43. 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...
  44. 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...
  45. 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
  46. 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?
  47. 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...
  48. W

    Can someone explain non-inertial reference frames

    What is a non-inertial reference frame? how is it defined?
  49. 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...
  50. 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)?
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