What is Inertial frame: Definition and 127 Discussions

In classical physics and special relativity, an inertial frame of reference is a frame of reference that is not undergoing acceleration. In an inertial frame of reference, a physical object with zero net force acting on it moves with a constant velocity (which might be zero)—or, equivalently, it is a frame of reference in which Newton's first law of motion holds. An inertial frame of reference can be defined in analytical terms as a frame of reference that describes time and space homogeneously, isotropically, and in a time-independent manner. Conceptually, the physics of a system in an inertial frame have no causes external to the system. An inertial frame of reference may also be called an inertial reference frame, inertial frame, Galilean reference frame, or inertial space.All inertial frames are in a state of constant, rectilinear motion with respect to one another; an accelerometer moving with any of them would detect zero acceleration. Measurements in one inertial frame can be converted to measurements in another by a simple transformation (the Galilean transformation in Newtonian physics and the Lorentz transformation in special relativity). In general relativity, in any region small enough for the curvature of spacetime and tidal forces to be negligible, one can find a set of inertial frames that approximately describe that region.In a non-inertial reference frame in classical physics and special relativity, the physics of a system vary depending on the acceleration of that frame with respect to an inertial frame, and the usual physical forces must be supplemented by fictitious forces. In contrast, systems in general relativity don't have external causes, because of the principle of geodesic motion. In classical physics, for example, a ball dropped towards the ground does not go exactly straight down because the Earth is rotating, which means the frame of reference of an observer on Earth is not inertial. The physics must account for the Coriolis effect—in this case thought of as a force—to predict the horizontal motion. Another example of such a fictitious force associated with rotating reference frames is the centrifugal effect, or centrifugal force.

View More On Wikipedia.org
Recent contents Top users
  1. S

    Simultaneous birth of two people in an inertial frame

    Suppose two people separated by some distance, were simultaneously born in an inertial frame that is moving at some velocity with respect to a stationary frame. For an observer in the stationary frame the two events are not simultaneous. The stationary observer will see one person is born...
  2. L

    Galilean Relativity and Newton's Laws

    I'm a little bit confused about the relationship between Galileo's Principle of Relativity and Newton's Laws. Indeed, as I understand, the Galilean Principle of Relativity is what Galileo presented with Salviatti's ship discussion. The discussion seems to lead to a simple idea: "if one performs...
  3. B

    Euler Angle from Body Frame to Inertial Frame

    Hi, This is not really a homework problem, but a project I'm working on. So, I am trying to build a Simulink model for my quadcopter. I derived the equations of motion using the Newtown-Euler method in the body frame to get transnational and angular acceleration. For the transnational part, I...
  4. Q

    Direction cosine matrix of rolling disk on circular ring

    Hey all, I'm stuck on this problem and not sure how to proceed/if I'm in the right direction. Problem: One reference frame N sits at the origin (inertial frame) while another frame, B, describes a disk rolling on a circular ring about the other frame. Picture below (A) find the direction...
  5. K

    Diffraction wavelength of particles in moving frames?

    Here's a question I cannot seem to comply with my understanding of Quantum Mechanics. The characteristic wavelength of a particle is responsible for diffraction interference fringes, which is part of the wavefunction solution to the schrodinger equation. But the wavelength of a particle is...
  6. PeroK

    Finding a Local Inertial Frame

    Homework Statement I am trying to find a local inertial frame for the following metric: ds^2 = -(1+\Phi(x))dt^2 + (1-\Phi(x))dx^2 I can get the transformed metric to equate to η at any point, but I can't get the first derivates wrt the transformed coordinates to vanish. Homework Equations...
  7. K

    Inertial frame of reference question for stacked boxes

    Hello, I was wondering about a question and how it would be reconciled within Newton's laws of motion. Take a case where two boxes are stacked on top of each other, and the bottom box rests on a frictionless surface. Now, imagine a rope is attached to the top box, and tension is applied to...
  8. adoion

    Was Einstein lucky when not considering twin paradox as paradox?

    hi, Einstein did not even consider the twin paradox as problematic at all, he argued that it is a simple consequence of his special relativity? obviously he never gave a explanation of why the two twins don't age the same he instead left it to others to do so. was Einstein just having a hunch...
  9. David Carroll

    Does acceleration change according to inertial frame of reference?

    I apologize if this has been discussed before. I am no physicist, I am just trying to see if I am understanding special relativity correctly. Please be advised I am dumb, so be gentle. If a spaceship (sorry for the cliché, but it's a little bit cumbersome to keep using the phrase "inertial...
  10. Satvik Pandey

    Relative velocity in inertial frame

    The swimmer will move in the direction of resultant of his velocity and velocity of water. Draw the diagram and the try to solve it.
  11. M

    The Earth: An Inertial Frame of Reference

    How Earth is considered to inertial frame of reference?
  12. 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...
  13. 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?
  14. H

    Constant Jacobian transformation of an inertial frame

    Suppose we do a constant Jacobian transformation (which is not Lorentz) of a SR (inertial) frame, by using four linear change of variables equations. This defines an apparent field with a constant metric (which is not the SR metric) in which there is relative acceleration of separation. From...
  15. J

    Rotation relative to an inertial frame

    Earth has a huge angular velocity regarding its rotation. Now let's imagine that the Earth has the velocity of 400 km/s relative to some inertial frame. What will be the velocity of Earth when we take the rotation into account combined with inertial motion? How do the 2 combine? Thanks in...
  16. L

    Transformation to local inertial frame

    I've been working on a problem that I can't seem to get started on. Here is how it is posted: Metric of a space is: ds^2 = (1+2\phi^2)dt^2 - (1-2\phi)(dx^2+dy^2+dz^2), where |\phi | << 1 everywhere. Given a point (t_0 , x_0 , y_0, z_0) find a coordinate transformation to a locally...
  17. L

    Pendulum in non inertial frame

    Homework Statement A pendulum is placed on a rotating platform which rotates with angular velocity ω around an axis, at equilibrium the angle between vertical and pendulum is θ θ= 20 degrees ω= 10 1/s how far is the pendulum placed from the axis Homework Equations...
  18. C

    Special relativity using inertial frame moving at 1/2u

    Quick disclosure, I'm only a few weeks into modern physics, and still trying to get a firm grip on the mechanics involved here. My understanding is that it is possible to use a reference frame that is moving, and this leads to a bit of a paradox, at least under certain conditions. Take two...
  19. 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...
  20. Z

    Relativity along an axis in an inertial frame

    Suppose that two events occur on the x-axis of an inertial frame, Δx apart with a time interval between the events of Δt. a) the proper time interval between the events is...? b) the proper distance between the events is...? I think I'm just getting confused by the wording. I imagined that...
  21. M

    Blackbody Radiation and Motion: Exploring the Dynamics of Inertial Frames

    I just confused myself with this idea, need someone to fix it please! Say a spherical black body temperature T is moving with velocity v in some direction through some medium with a lower temperature. In the sphere's rest frame this emission is isotropic, however, in the rest frame of the...
  22. W

    Can anyone explain the use of inertial frames for problem solving in E&M?

    Can anyone refer me to a discussion of applying the technique of changing reference frames to problem solving? Why it works, and what it means. I'm familiar with using it in some E&M problems, but I guess I don't really "get" it. For example a particle in an E&M field has m\vec{a} =...
  23. K

    Definition of Inertial Frame in GR: Math Explained

    How do we mathematically define a inertial frame in GR? Is it only a basis in some tangentspace or does it have to be induced by a coordinatechart? :/
  24. 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!
  25. J

    Velocity change by force in one and two inertial frame confusion

    Hi, I just finished class and my professor was writing some of Newton's Laws on the board and derived some equations. We ended up with: V(Δt)=FΔt (this is for velocity in first inertial frame V(2Δt)=2FΔt (this is for velocity in second inertial frame Then he went and got the position in...
  26. P

    Newton's law in non inertial frame.

    Please explain the concept of pseudo forces by considering an example of two cars say A and B, accelerating in the same direction. How will Newton's law applied to the man in car B as noted by the man in car A differs from that of the man standing on the earth? And how will the man in car A...
  27. J

    Can we extend our inertial frame globally?

    People tell me that we cannot extend our inertial frame, as defined in special relativity, across the Universe because that would be in violation of general relativity. The problem is that general relativity says that space-time can be curved whereas a global inertial frame assumes flat...
  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. N

    Origin in Inertial Frame for Spin-Orbit Coupling?

    Hello, I've seen spin orbit coupling being explained by going to the rest frame of the electron and noting that the proton is then a moving charge and hence has a magnetic field, which interacts with the spin of the electron, effectively coupling the spin and angular momentum of the electron...
  30. M

    Isotropy/Homogeneity of Spacetime and Inertial Frame Equivalence

    So this is problem 11.1 out of Jackson Electrodynamics: Two equivalent intertial frames K and K' are such that K' moves in the positive x direction with speed v as seen from K. The spatial coordinate axes in K' are parallel to those in K and the two origins are coincident at times t=t'=0. (a)...
  31. P

    Why so many definitions of an inertial frame?

    A Newtonian inertial frame is one where objects obey Newton's first law. Schutz (A first course in general relativity) says an inertial frame cannot be constructed in a gravitational field because it's then impossible to synchronize the frame's clocks? For the same reason an inertial frame...
  32. 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...
  33. S

    Pendulum on Pendulum, velocity in non inertial frame

    Homework Statement A double pendulum consists of two particles of equal mass m suspended by massless rods of equal length l. Assuming that all motion is in a vertical plane: 1. Find the Lagrangian of this system. 2. then find the equations of motion and, 3. linearize these equations...
  34. S

    Acceleration measured in another inertial frame?

    Suppose, in the first case, that an object (initially at rest in frame S) accelerates, for whatever reason upward, with a force F. Let M be the relativistic mass of the object. The force measured in frame S is relativistically given by: F_s=γ^2...
  35. E

    Definition of local inertial frame

    I have a question I wanted to clear up. According to the definition of a "local inertial" frame in GR, you must use a coordinate system that locally looks Cartesian, right? I mean if you had a coordinate system with a basis that wasn't orthogonal, then it would not be considered a local inertial...
  36. M

    Inertial frame dependent on mass?

    My question is: Is the inertial reference frame dependent on mass? In re-reading materials on the topic of special relativity, I have noticed something that passed my attention previously. Within the inertial reference frame, the mass of test particles isn't necessarily dependent on how they...
  37. L

    Non inertial frame: Speed of light

    The speed of light is not constant in a non-inertial frame; the light accelerates with the acceleration of the observer in reverse direction. Consider the following problem: If a light pulse is created in an inertial frame at some time, t<0 (say t=-10); the light pulse moves at velocity c...
  38. D

    What Determines the Speed of a Spacecraft in Special Relativity?

    Homework Statement Usually in physics problem on special relativity, the state that this particular spaceship is traveling at, say, 0.6c. Question is, where does this 0.6c come from? If the speedometer in the cockpit reads 0.6c, does it mean that the observer will look and think that it...
  39. 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...
  40. Y

    Let a clock A be at rest in an inertial frame and let a clock B rotate

    Let a clock A be at rest in an inertial frame and let a clock B rotate around it with constant velocity and constant distance from A. Let v be the velocity of B relative to the inertial frame. Both clocks count how long it takes for B to rotate once. According to clock A, the time it takes is...
  41. V

    Will the frame be inertial if no forces act on it?

    Hello :) An object is placed far away from all the bodies that can exert force on it. A frame of reference is constructed by taking the origin and axes fixed in this object. Will the frame be necessarily inertial? Hmm According to me, it should be an Inertial frame as No force acting on it...
  42. M

    Is a point (x distance from earth) inertial frame ?

    me and my friend were arguing (like always) about inertial frame ? to sum up i m just asking a straightforward question ? let say (for simplicity) there is just Earth and an other object in whole universe. a point whose distance from Earth is x. and dx/dt = 0. now is that point (which...
  43. 1

    Why do we treat earth and why does it work as an inertial frame

    Earth is clearly not an inertial frame, its in orbit and not following a single direction of movement. Why then do we treat it as one? Are there any slight differences in the laws of motion in a true inertial frame in contrast with those on earth?
  44. P

    Block sliding down accelerated inclined (need inertial frame approach)

    Homework Statement A block of mass "m" is placed on an incline of angle \theta and mass "M", which is placed on a horizontal surface (the ground) and release from rest. Both the block and incline start accelerate. All surfaces are frictionless. Find the acceleration of the block with respect...
  45. R

    Coriolis Acceleration and Inertial Frame

    Hi In my textbook they were doing a derivation of the acceleration of a projectile flying on Earth. Although they used the center of the Earth as the frame of reference, they ended up with the linear combination of 3 quantities for the acceleration of the projectile, one of which they said...
  46. P

    GR: Local Inertial Frame & Poincare Invariance

    Is it possible to deifine local inertial frame which is Poincare invariant (in general relativity) (every manifold is locally flat, so we can chose coordinates which are almost pseudoeuclidean, but in what sense they might be Poincare invariant) Thanks.
  47. 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!
  48. e2m2a

    Torque relative to an inertial frame

    I have a thought experiment I cannot resolve. Maybe someone smarter than I can resolve this. Suppose we have a long, thin rod, rotating in the counter-clockwise direction around a pivot axis which is at the end of the rod with an initial angular velocity equal to w. The axis is connected to a...
  49. 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.
  50. G

    Confusion about a laser shining perpendicular to a moving inertial frame

    I found this nice book on Google http://tinyurl.com/yh2y2zb that does a great job explaining relativity, however, even though the conclusions make perfect sense to me so far, I'm stuck on a conceptual issue when reading over the classic thought experiments that makes me feel like I'm still...
Back
Top