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.
Homework Statement
Suppose a frame S' is related to S by a boost in the y direction by v. Imagine a wall is at rest in the S' frame along the line y'=-x'. Consider a particle moving in the x'y' plane that strikes the surface and is reflected by the usual law of reflection θ'i=θ'r. Find the...
Homework Statement
The figure shows a rigid assembly of a thin hoop (of mass m = 0.25 kg and radius R = 0.13 m) and a thin radial rod (of length L = 2R and also of mass m = 0.25 kg). The assembly is upright, but we nudge it so that it rotates around a horizontal axis in the plane of the rod and...
I should preface this question by saying that I am not familiar with Einstein's general relativity, so I am trying to understand the relationship between gravitational and inertial mass from a purely classical standpoint.
Newton writes that the gravitational force exerted by an object is...
When I was surfing on a group in Facebook, I found two concepts very difficult to understand by reading the discussions in comments. Those concepts are inertial and non inertial frame of reference. Please make me understand these two concepts in simple words. Please don't suggest links as I...
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...
Hi All
Physics newbie here...
Just a quick question regarding Inertial and Non-Inertial Reference Frames.
From what I understand:
Inertial = One that obeys Newton's Law of Inertia. Moves at constant velocity in one direction
Non-Inertial: One that accelerates.
Right?
So, I read somewhere that...
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...
In class we had a conceptual problem:
There will be a race between two springs. Both will receive the same initial impulse, but one has been agitated and is therefore oscillating in some way, the other is just still. Who arrives first?
The answer is that the still spring arrives first because...
I've attached an image to a conceptual problem I'm having a little trouble understanding. It shows part a, b, c, and d (but d is cut off). a and b are one inertial frame while c and d are another. c and d makes sense, but I'm having a little trouble with a and b. Based on the image for c, there...
I'm reviewing physics after ~30yrs of neglect, starting with Halliday & Resnick (and the internet).
Here's what I understand to be standard Newtonian/classical inertial frames:
1. There exists a set of reference frames, called inertial frames, in which mass, time, force, acceleration, etc. are...
What is the definition of an inertial frame ? I've read that Inertial frames are reference frames in which Newton's first law applies (i.e.bodies subject to zero net external force moves at constant velocity) , however Newton's 1st law itself is only valid under inertial frames. I find it weird...
Homework Statement
Let S and S' be two inertial frames of reference where S' is moving at a velocity of 0.6c relative to S.
When x = x' = 0, t = t' = 0, where t and t' are time of the clocks on S and S' respectively and x and x' are the x-coordinates of the S and S' frames respectively.
An...
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...
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...
I have a 3-pack of related relativity musings I was hoping someone(s) could enlighten me on:
1) Since the reach of gravity is infinite and the universe is homogeneous and isotropic with regards to the distribution of matter, is it fair to say that no object, even those in deep interstellar or...
Homework Statement
A point P is emitting a bundle of photons. In inertial system I the opening angle of the bundle is d\Omega which hits a plane at a distance R. The same process is being observed by an inertial frame I' moving wrt. I.
Show that: R^2d\Omega=R'^2d\Omega'
Homework Equations /...
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...
Inertial forces are not real, but apparent forces that are experienced by an observer in a non-inertial reference frame, reflecting the motion of the frame. Thus, you experience a backwards inertial force if you sit in an accelerating car, and a forward intertial force if the break is applied...
Homework Statement
Not a homework or coursework question, but given the simplicity of the problem I feel that this is an appropriate subforum.
Consider a person spinning a rock on a string above their head at a constant angular velocity, walking away from the observer at a constant linear...
I'm interested in applying inertial navigation over a very small range < 2 meters. Everything I have seen so far that is related to using inertial navigation for dead reckoning is for very large scales and gives accuracy on the order of fractions of miles or several feet. Does anyone know what...
Hi all!
I have a question that maybe some people of this great comunity can help.
I´m working with a platform with 16 MEMS accelerometers distributed along the whole surface with a knew position and orientation, I have to measure the differences in acceleration on the Z axis, to get the surface...
Hi everyone,
I read in a first year textbook (K&K) that the reason why "gravitational mass is proportional to inertial mass" is a big "mystery"...
Can someone please explain why this is a mystery?
Thanks
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...
A ball of mass 'm' is inside of a tube that rotates in a horizontal plane around the vertical axis (Drawing a circunference). Attached to the ball (inside of the tube) there is a massless, inextensible rope that goes to the midpoint of the circle described by the rotating tube. The other end of...
I'm wondering if someone is observing a situation from a frame moving in a uniform circular motion, would that frame of reference be considered inertial? I'm unsure because of the centripetal acceleration towards the center.
is it possible by any means to use a type of resonance wave to convert the vibrating motion of molecules in an object such that they start moving in the same direction causing the object to take off at high speed once the majority of the molecules are moving in the same direction?
the...
When neglecting gravity and body size, if a body rotating at uniform angular velocity about a central body sends a light signal to the central body, the central body will receive the wavelength as longer by 1/γ. Conversely, if the central body sends a signal to the rotating body, the rotating...
Hi:
I'm building a computer simulation for a 3 gear train system. So far the gears rotate with mouse movement horizontally. Now I'm adding a fictitious motor and braking system to start/stop rotation with mouse clicks. I multiplied the rotation angle by [1-e(-t/TC)] to simulate exponential...
Or stated otherwise:
Is it possible, due to other effects than mass for a non-spinning object with inertial mass n to exert a gravitational force characteristic of another non-spinning object with inertial mass different than n - theoretically or practically?
I hope that covers all the caveats...
Let me set the stage for a thought experiment.
1. A physicist in an elevator at some arbitrary height above Earth holding an accelerometer oriented in a direction pointing toward the center of the Earth.
2. No atmospheric drag.
Drop the elevator car and make a measurement. The...
According to Einstein (e.g. in his book The Meaning of Relativity), a clock rotating about a central clock will be judged by the central clock to run slower than the central clock.
This means that a signal sent by the central clock will be perceived by the rotating clock as being of a higher...
Hello guys, I just had to ask a quick question about the nature of light. In different synchronization parameters regarding inertial frames (other than 1/2) light can take value between c/2 and infinity. So far, so good for inertial frames. But considering non-inertial frames, what are the...
When the 2nd order ODE (ay''+by'+cy=0) is taught, is said that the elastic force is proportional to displacement and that the damping force is proportional to velocity, but I never heard the following proposition: "the inertial force is proportional to acceleration (and the constant of...
Homework Statement
Prove inertial force is potential force.
Homework Equations
$$\mathbf{F}_i=-\nabla V_i$$
The Attempt at a Solution
$$\oint \mathbf{F}_i\cdot d\mathbf{r}=0$$
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...
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?
Einstein has a thought experiment with two trains which he uses to prove linear motion without acceleration is inertial. Inertial means there is no physical test which will prove which train is moving and which is stationary, no coordinate system is preferred and that coordinate system are...
So I was told that a pseudo-force acts on a body when its's motion is analysed with respect to a non inertial reference frame. I'm a bit confused. Does that mean the reference frame is accelerating with respect to the body, or with respect to the earth? And why does there have to be any sort of...
Suppose that we have a body that is moving at a straight line, inertially wrt to another frame. If it starts to move in a circular way after that, what can be said about the motions of its points. Do all points have to deccelrate to achieve the circular motion, but in a different manner, since...
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...
I was just wondering what would the definition of the inertial frame be, since as I've understood the description it seems that an inertial frame seems to be 'free' from any external forces, correct me please if I'm wrong. Can something be an inertial frame even if gravity acts upon it? For...
it was mentioned in another thread that only inertial forces are frame dependent or relative.
what is an inertial force?
what are the differences between inertial and non-inertial forces?
and most importantly:
why inertial forces are frame dependent while other forces are not?
i tried...
Homework Statement
So I'm having some trouble understanding this paragraph from my textbook. I was hoping that maybe someone could explain it to me.
For example, we can assume that the ground is an inertial frame provided we can neglect Earth's astronomical motions(such as its rotation)...