Frame Definition and 1000 Threads

A vehicle frame, also historically known as its chassis, is the main supporting structure of a motor vehicle to which all other components are attached, comparable to the skeleton of an organism.
Until the 1930s, virtually every car had a structural frame separate from its body. This construction design is known as body-on-frame. By the 1960s, unibody construction in passenger cars had become common, and the trend to unibody for passenger cars continued over the ensuing decades.Nearly all trucks, buses, and most pickups continue to use a separate frame as their chassis.

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  1. S

    I Does the CMB reference frame violate the Cosmological Principle?

    Studies of the Cosmic Microwave Background shows that the Earth is moving roughly 380 km/s with respect to it towards the constellation Leo I think. Yet (I think) the Cosmological Principle and the Michelson-Morely experiments suggest there is no preferred reference frame in the universe --...
  2. L

    B Inertial Frame of Ref & Forces: Understand Special Relativity

    In trying to understand a bit of special relativity, I want to make sure if I understand it correctly, and I came up with the following question: "Imagine you would know all forces in the universe acting upon an object, doesn't that give away the only real existing frame of reference (imagining...
  3. cianfa72

    I Principle of relativity for proper accelerating frame of reference

    Hi, I've a doubt about the application of the principle of relativity as follows. Assume as principle of relativity the following statement: It is impossible by any experiment performed inside a "closed" laboratory to say whether we are moving at constant velocity or staying at rest. Consider...
  4. RUTA

    Insights No Preferred Reference Frame: Quantum Mechanics Interpretations

    Continue reading...
  5. Arman777

    Why are all values NaN after mapping 'player_name' column in Pandas Data Frame?

    I have two data frames df1 and df2 df1 has two columns 'player_name' and 'player_id'. Similarly df2 has 'player_id' column. From this configuration I want to pass 'player_name' column to df2 by using 'player_id'. For this reason I have tried something like this, df2['player_name'] =...
  6. yucheng

    Restrictions on the frame of reference

    Newton's laws only hold in intertial frames. In general, the center of mass (CM) is accelerating, so it cannot be used as a frame. However, 1. Suppose that CM is accelerating only in the ##\hat{z}## direction. Does this mean that the CM frame is still valid in the ##\hat{x}## and ##\hat{y}##...
  7. D

    Rotation: inertial frame vs. body-fixed frame

    Hi Angular momentum L is related to the moment of inertia (MOI) , I by L= Iω In the body-fixed frame , ie. rotating with the object then ω = 0 and so the angular momentum is zero in the body-fixed frame. Is that correct ? If i have a thin circular ring then the MOI about the centre is given by...
  8. SilverSoldier

    Thermal Expansion of a Triangular Frame

    Suppose each side has initial length ##l##. The solution taught to me is as follows. Considering the lengths of the rods after expansion, we write $$\dfrac{3l^2}{4}\left(1+\mu\theta\right)^2+\dfrac{l^2}{4}\left(1+\alpha\theta\right)^2=l^2\left(1+\lambda\theta\right)^2$$ according to the...
  9. F

    Body-Fixed Reference Frame -- How is it useful?

    Hello Everyone, I am trying to understand the usefulness of a body-fixed (body-centered) frame of reference ##O'x'y'z'## versus a lab frame of reference ##Oxyz##. The body-fixed frame is attached to the moving body and changes orientation exactly as the body changes orientation. From the...
  10. B

    Frame indifference and stress tensor in Newtonian fluids

    During lecture today, we were given the constitutive equation for the Newtonian fluids, i.e. ##T= - \pi I + 2 \mu D## where ##D=\frac{L + L^T}{2}## is the symmetric part of the velocity gradient ##L##. Dimensionally speaking, this makes sense to me: indeed the units are the one of a pressure...
  11. L

    Help calculating the current from the density and a rotating frame

    hi need help in physics HW: given current density [J][/→]=[J][/0][x][/Λ] and rotating frame with given surface vector: $$ A^→ = A_0(cos(wt)x^Λ + sin(wt)y^Λ$$ in need to calculate I(t) i tried I = ∫J*dA but i don't know i to technically do the math please help me
  12. F

    Reference frame in collision problems

    2 balls (Ball 1 and Ball 2) collide fully elastically and their relative velocity stays the same as but in sign opposite to that before the collision. Is there any sort of reference frame in which Ball 2 is always fixed (at rest) so that one can look at their relative velocity always in that...
  13. F

    Whether a non-inertial frame is absolute

    If a frame is a non inertial frame, then it must have an acceleration. Then which reference frame is this acceleration with respect to? If this acceleration varies with the reference frame this acceleration is calculated with respect to, is this non inertial frame absolute?
  14. P

    A Transmission Line in Accelerating Frame: Energy Conservation Puzzle

    While I believe I have an answer to this problem, I think it's an interesting one and counter-intuitive. I think it might spark some interesting discussions. The bow of a Born rigid accelerating spaceship has a proper acceleration of g. There is a transmission line running from the stern to...
  15. X

    Is Coulomb's law valid in a non-inertial frame?

    Hi, I was wondering, if the charges do not move in a non inertial frame and I don't move too in this frame, will I see the same Coulomb force, some fictitious forces and radiation coming from these static charges? Thanks!
  16. cianfa72

    I Reference frame vs coordinate chart

    Hello, here on PF I've seen many threads about the concepts of 'reference frame' and 'coordinate system'. In the context of SR my 'envision' about the concept of 'frame of reference' is basically the 'rods & clocks latticework' as introduced in the book Spacetime physics (Taylor, Wheeler)...
  17. D

    How Much Force Is Needed to Topple a Frame on Castors?

    Hello all, I'm trying to calculate how much force is required to topple over a frame with a conveyor attached to it. I have attached a screenshot of the assembly. I have the centre of gravity as seen on the screenshot. The two lines to the pivot points show the angle. These are 16 degrees (line...
  18. LCSphysicist

    Proper time in an acceleration frame

    $$d\tau = \sqrt{-g_{\mu v}\frac{dx^{\mu}}{d\lambda} \frac{dx^{v}}{d \lambda}} d \lambda $$ Calling ##d \lambda = d t##, t is coordinate time in an inertial frame. $$\Delta \tau = \int \sqrt{-(-1+v^2/c^2)} dt$$ $$\Delta \tau \approx \Delta t - \frac{g^2*\Delta t^2}{6c^2}$$ where $$\Delta t = 2...
  19. D

    Engineering Steel Frame Connection: Design and Moment Considerations

    Hi All, this is a steel frame , top beams sitting on top of column with steel plate cantilever at both sides (one side longer than the other) , so there will be hogging moment at the center support. However, the top steel beam is one whole piece, does the connection between the steel beam and...
  20. Athenian

    [Special Relativity] - Finding the Proper Length at Rest in Frame S'

    Currently, the only part of the textbook question that is completely throwing me off is "an angle of ##l=\sqrt{2}c##". If I am not mistaken, how am I suppose to interpret that as an angle and calculate for the answers of (a) and (b) accordingly? As for my attempted solution process of this...
  21. bq1892

    Describe the length of an electron's journey in its own frame of reference

    Lv = Lo / γ 1/γ =√(1-v^2/c^2) = √(1-0.8^2) = 0.6 Therefore Lv = Lo x 0.6 = 150 x 0.6 = 90m Therefore electron travels 90m in its own frame of reference (answer key solution) However, shouldn't the electron be assigned rest length, Lo, as its frame of reference is at rest with itself instead...
  22. jay_chay22

    Engineering Frame and Machine (engineering mechanics statics)

    I have problem on this question on how to draw free body diagram. Can you please show me on how to draw free body diagram on this question ? The calculation part I think I do not have a problem with it. Thank you in advance ! I am really struggle with this question.
  23. E

    Elevator Frame Design: Can It Stand Alone?

    Hello there, I am wondering, if I were to build an elevator in a building, is it possible if I build the elevator frame (and rails) without using the rail bracket? The weight of the cart plus the contents would be supported by only 4 steel columns fixed to the ground. I know it is a silly...
  24. O

    Lorentz transformation of multiple events into one frame of observation

    The three events; t = 0s, x=0 t=1.3s, x=1.3 light seconds t=2.6s, 1.3 light seconds
  25. A

    Can Mechanical Energy Be Conserved in an Accelerated Frame?

    In the frame of the accelerated block, I applied the non-inertial force F'. My doubt is if I can conserve the mechanical energy in the accelerated frame and find the speed at the top. Otherwise, how could you proceed.
  26. kmm

    I Observing Black Holes in Finite Time

    My understanding from General Relativity is that if as distant observers we watch a probe or any test mass approach a black hole, time dilation goes to infinity as the probe gets closer to the event horizon. This would imply that we would never observe a black hole form, or the collision of two...
  27. Leo Liu

    Is angular momentum conserved in a non-inertial frame?

    Question: If we place the frame of reference on an accelerating point, does the total rotational momentum still remain the same? I attempted to solve this question by manipulating the equations as shown below. $$\text{Define that }\vec r_i=\vec R+\vec r_i'\text{, where r is the position vector...
  28. G

    Confirm if I'm Correct? "Page 49 Q: Time in Moving Frame?

    Because the book doesn't have an answer. Can someone confirm if I am correct? The question can be found on page 49 of the link below. I added arrows to the picture just to separate the equations not to say greater then. https://scholar.harvard.edu/files/david-morin/files/relativity_chap_1.pdf...
  29. roybot

    Motion-powered GPS tracker to install permanently inside a bicycle frame

    Briefly, the problem; stolen bicycles are notoriously difficult to recover. Designing a GPS tracker to fit on one is challenging, because bicycles rarely have their own available power source. Whatever GPS unit is used must typically have its own battery as its sole source of power, which...
  30. F

    B Will You Capture Jupiter and Saturn's Historic Conjunction?

    https://phys.org/news/2020-11-december-jupiter-saturn-planet-middle.html I do not know if we have enough hobby astronomers here, but the above calls for a photo competition. But in any case, don't miss the opportunity if you're a stargazer!
  31. F

    I Gyroscope, Gimbals Frame, lack of precession

    Hello, A simple gyroscope, which is nothing but a spinning top, will exhibit precessional motion if a) it spins and b) a nonzero gravitational torque is applied to it. The tip of the gyroscope rotates while the tip rotates on itself. If the gyroscope is mounted on gimbals, which are rings, the...
  32. W

    B Difference between an Einstein frame and a String frame?

    I have listening to talks come across the terms"Einstein frame" and "String frame" but am not at all clear what they mean. Can anyone give a layman's explanation as to what is theses phrases mean in the context of cosmology ?
  33. e2m2a

    B Frame Dragging Rate: Mass Proportionality?

    Curious about frame dragging. Is the rate at which frame dragging occurs proportional to mass? For example, when the Earth rotates it has been confirmed space drags with the earth. I assume the rate is very small compared to the rotation rate of the earth. However, if the mass of the Earth...
  34. S

    Rotating body viewed from its own rotating ref. frame, then perturbed

    Pondering over this thought experiment, a question comes to mind -- to which my brain sometimes replies "of course" and sometimes "no way!"A disk shaped satellite ("in zero-G") spins about its axis. There are two thrusters mounted as shown on two axial booms. The thrusters are fired briefly at...
  35. thequantumcat

    I Special Relativity and Velocity

    I can't seem to wrap my head around it: if an object is moving at speed v in frame S, and its observed to move at speed v' in S', what is the relationship?
  36. J

    Frame of reference question: Car traveling at the equator

    Earth rotate from west to east with 460m/s at equator. Car travel at equator from east to west at speed 460m/s. 1- What is car speed from inertial ref.frame? zero?How is zero if car travel in curved line? 2-What is car speed from rotational frame ? 3-How much is car weight,compare to car...
  37. M

    Equations of relative motion with respect to a rotating reference frame

    Hi, I am just writing a post to follow up on a previous thread I made which I don't think was very clear. The question is mainly about how to use the below equations when there is also a rotation of the body around the fixed reference point. Please see the diagram here to see how the vectors...
  38. V

    I Momentary Co-Moving Reference Frame in SR

    In SR, for the momentary co-moving reference frame, U (the velocity four vector) takes the form (1,0,0,0). I'm wondering whether the basis vectors associated with this velocity are zero or if the coefficients in front of the basis vectors are zero. In classical mechanics we would say that the...
  39. M

    Question about Formulae for Motion in a Rotating Reference Frame

    Hi, I am reading the following question: "Particle P moves in a circular groove with radius ## a ## which has been cut into a square plate with sides of length ## l ##. The plate rotates about its corner ## O ## with with angular velocity ## \omega \hat k ## and angular acceleration ## \dot...
  40. U

    I Fixing orientation by fixing a frame in a tangent space

    I would like to show that fixing the orientation of k-manifold smooth connected ##S## in ##\mathbb {R} ^ n ## is equivalent to fixing a frame for one of its tangent spaces. What I know is that different orientations correspond to orienting atlases containing maps that cannot be consistent with...
  41. K

    B Earth Center of Mass: GR & Inertial Object Acceleration

    Super-basic question that I'm embarrassed to ask. It's just what the summary says: Taking Earth's center of mass as our reference frame, how does GR account for an inertial object near the surface approaching with an acceleration of G? I assume (perhaps incorrectly) that this is an inertial...
  42. Haorong Wu

    I Acceleration Frame in SR: References for Research

    Hi. I am looking for some references of acceleration frame in SR, such as an accelerating rocket problem. I have some equations regarding the time, distance, velocity measured in the Earth frame, etc. But the reference I have does not provide the derivation of those equations, so I need some...
  43. J

    I The Twin Paradox implies that the Universe as a whole is a special frame

    The Twin Paradox implies that the universe as a whole is a special frame of motion according to "Relativity Simply Explained" by Martin Gardner. I want to be sure than I haven't misunderstood something. I don't find the explanation completely clear. If the universe as a whole is a special and...
  44. H

    I The reference frame for angular momentum components

    In which coordinate system the components of angular momentum are quantized? Better to say, if we can select the coordinate system arbitrarily, how the components of angular momentum, say z-component, are always ##L_z=m\hbar##?
  45. Livio Arshavin Leiva

    Rectilinear movement seen from a rotating reference frame

    Let's suppose there's some platform that is rotating with angular speed omega and has a radius R. At t=0 we release some object from the border, which has an initial speed perpendicular to the radius direction with magnitude \omega R and we want to know its position at t=T with respect to the...
  46. mingyz0403

    Engineering Did I Make a Mistake in Solving for the Load Applied at Point D?

    My answer was correct, however my direction was different from the textbook. I have checked my work a few times ,but not able to find out what I did wrong. Could anyone tell me what I did wrong. Thank you in advance for your help.
  47. E

    Dropped object in a rotating frame

    I solved this in an inertial frame, but now I want to do it in the rotating frame. As far as I can tell the equation of motion is $$\vec{F}_{cent} + \vec{F}_{cor} = mr\omega^2 + 2m\vec{v} \times \vec{\omega} = m\frac{d^2\vec{r}}{dt^2}$$The solutions take a different approach. They state that the...
  48. D

    B Time dilation and the reference frame of the vacuum

    The point of the twin paradox in special relativity is that the traveling twin experiences a real, frame-invariant effect in which the time evolution of all moving matter is slowed down. If you read a hundred articles and textbooks on SR, you'll see a hundred variations on the message that the...
  49. D

    A Reference frame of the vacuum -- which forum?

    I have a question about interactions between matter and the vacuum, but I don't see a forum for that. Quantum field theory seems to be the most closely related subject. What would be the best forum for questions related to QFT?
  50. T

    What is an inertial frame? A conflict of two definitions

    Good Morning (I see this has been discussed here, but I am more interested in two specific definitions and whether the conflict.) I had always thought that the definition of an inertial frame was: "A frame in which Newton's Laws are valid." A person has been arguing with me that the definition...
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