4.3 Reference Frames

MIT 8.01 Classical Mechanics, Fall 2016
Instructor: Prof. Deepto Chakrabarty

License: Creative Commons BY-NC-SA

[marrytesfu]

How can an amazing explanation like this get low views. Without any hesitation the best explanation on the topic !!!

[wujufella]

simple, succinct, nuanced. this video is amazing. its a shame that most professors cant just be straightforward like this. theyd rather spend 2 minutes teaching it poorly and re-explaining it over and over rather than just putting a good 10 minutes aside to nail the topic. thank you for these videos you are saving my life.

[isagumus]

Literally couldn't be a better use of technology and materials! Amazing explanation.

[ahmadeldesokey]

Best explanation on youtube. Thanks MIT❤❤

[mamunsuhayel]

Thanks MIT.. It's the best explanation of transformation of inertial frame....
But why this videos have this small like?...

[adhavankadhiravan]

The best explanation for Inertial frame of reference.

[jacobzetterfeldt]

Simply amazing! Thank you for such a great explanation(:

[ravn]

but adding |r'> makes no sense in frame S as it is described by another basis in frame S', so adding |r'> added to |r> = |R> + |r'> feels wrong

[cafe-tomate]

How are we allowed to use F=ma in the second referential ? It's a moving referential.

[pratikkumarbulani]

At 5:48, why is the dr/dt not equal to 0?

[NH-zhmp]

Hi sir, I am a mathematics student who are interested in the concepts of spacetime in relativity theory and quantum mechanics with a rigorous mathematical background. Recently I've been self-studying the topic of spacetime in relativity theory, and the first thing to understand clearly is the inertial frames.

So I started with ithe nertial frames in Galileo-Newton classical mechanics. In the book "An Introduction to Riemannian Geometry With Applications to Mechanics and Relativity" of authors Godinho - Natário, page 252, they present a definition for inertial frames as follows :

" Let M be a smooth manifolds and diffeomorphic to R4. We assume that there exists a special class of diffeomorphisms x : M → R4, p ⟼ x(p) = (t, x1, x2, x3)(p) called inertial frames. A special class of motions is formed by the motions of free particles, i.e. particles which are not acted upon by any external force. The special property that
inertial frames have to satisfy is that the motions of free particles are always represented by straight lines. In other words, free particles move with constant velocity
relative to inertial frames (Newton’s law of inertia). In particular, motions of particles at rest in an inertial frame are motions of free particles. "

What do you think about this definition of inertial frames, is it clear enough to be able to used ? I' haven't got it well yet, I wonder what is the "free particle" is defined by mathmematics in detail ? I know that the if a particle is free in one inertial frame then it is also free in other inertial frames, but I don;t know that is a condition in the definition or it is a theorem ... Because if free particles are defined as the particles under zero external force, then I can give some example of free particles that are not represented bt stright lines in an inertial frames.

E.g, let M = R4, consider the diffeomorphism id : M → R4, id(p) = p, this is a stay put inertial frame. Let a free particle be modeled by the motion α : [0, 1] → M, α(s) = (s^2, s, s, s). The motion of this particle in the inertial fram id is given by id ∘ α (s) = α (s) = (s^2, s, s, s). It's clear that the acceleration of this particle is (0, 0, 0), thus the external force acts upon it is zero, which mean it must be exactly a free particle. But this particle's motion is represented by the curve (s^2, s, s, s) in the inertial frame id, which is not a stright line.

May you give me an explanation for my struggling ? Thank you

[JimJWalker]

Nothing in the universe exists in motion without any forces acting upon it. So, how can you know if Newton is correct? You cannot create an experiment to test it. You can make more and more accurate predictions and measurements, but you will never know for certain because you are using idealized conditions.

[georgejohny]

Sir in 4:43 you said that r prime will appear to be in motion because the distance between the observers changes. What if the S prime observer is moving in a circular path?

[harmankashyap]

anyone clear my doubt please

What if the net force on some particle is zero and we choose that particle itself as the reference frame or frame moving uniformly relative to the particle. whether we can call that frame an inertial frame of reference?

[hks]

MIT is improving the world by providing free education. Meanwhile my school doesn't even give students soft copy of our lecture notes and tutorials and doesn't give access to lecture videos of higher order subjects to everyone

[nataliortman]

I’m really not understand how this system has a acceleration if it is inertial system. Please explain for me ❤

[abcddd]

what does it mean if "the coordinate axes in frame S' are parallel to, but displaced away from the coordinate axes in frame S"? Also, is the object moving from the origin of Frame S to where it is shown in the video?

[i_am_Tejasv]

Can anybody tell me on what and with what is he writing?

[shibaneethakur]

Sir which book you have preferred for this

[johnblacksuperchemist]

I am confused and no one will help me. (1) I am told there is only ONE type of inertial frame of reference. (2) meaning if i do a physics experiment in ANY inertial frame i will get the SAME RESULTS no matter what inertial frame i am in (3) I am told earth is an inertial frame. (4) I am told being in outer space at a constant velocity is an inertial frame. OK THESE STATEMENTS CONTRADICT ONE ANOTHER Because if that were ALL true then that would mean that i could do physics experiments in outer space (at a constant velocity) and then do the SAME PHYSICS EXPERIMENT on earth and get the SAME RESULTS. But that IS NOT TRUE. THAT IS A LIE. If i am in outer space(at constant velocity) and i hold a ball out and let go of the ball with out throwing it or pushing it in any direction the ball will just float there. But on earth if i do the SAME experiment the ball will fall to the ground. So there are (1) more than one TYPE of inertial frames of reference OR (2) earth is NOT an inertial frame of reference. SO WHICH IS IT Why wont any one answer