Einstein's Equivalence Principle (Problem 31)

Einstein's Equivalence Principle (Problem 31)

[Martyr]

I like how you apologized for something I never even noticed. You're forgiven. :)

[guyfromkerala]

Professor I read that its difficult and takes much time creating video suggest brilliant.org where u can post ur problem to thousands of students ....u can write help or solution to problems by is really nice consider it Professor

[esa]

I find this basic idea behind General Relativity so simple and elegant, that it takes a genius to invent it. From this follows that gravity is actually a fictious force, like centrifugal force. It is actually the floor that is pushing you up, while space keeps falling inside Earth. It is just a matter of frame of reference, but for me it means freeing your mind to understand more than your everyday experiences.

[hanslepoeter]

Think my solution was a bit more simple then anyones, I converted mass of the total pully to mass on the outside and just added that to the weights.
Another thing : I'm a home brewer and noticed a usefull diy device called the ispindel. As you are aware beer and wine are mostly a mixture if water, alcohol and sugar. Change of specific weight of the liquid during fermentation is an indication of how much alcohol is formed.
This ispindle is like a big sealed test tube with some electronics. You throw it in the fermentation vessel. How much it floats slanted is an indication of the specific weight ( and communicated over wifi ).
Now here's the big question : What is the relation between the slanted angle and specific gravity. ( center of mass, diameter, length maybe and weight come into play as well I think. ) specific weight of beer is between 1200 g/l( max ) and 990 g/l ( min ).
Interesting is what parameters would give me the maximum swing for this thing, so it reaches maximum accuracy.
I'll have a go at it myself, i don't expect you to solve it for me. Also limits for all parameters apply which i have not figured out yet. .
However it might be inspiration for a Lewin problem. I'ts not an easy question. Feel free :-).

[yabhishekreddy]

Hello professor. Your lectures are incredible. I am an electrical engineering graduate from India. How deep should we dwell into physics to understand electrical engineering? We study machines, power systems etc etc, but I feel they are quite abstracted and doesn't deal with all the physics and math background done behind it.

[vinodkumarchauhan]

Are u real WALTER LEWIN... YOUR LECTURES ARE SUPERB

[nicholasbudenberg]

You are forgiven and we will still be friends. :)

[ramzankhanbarech]

Sir you really worked in physics. Love you Sir from Pakistan

[harikishan]

I just had a crazy thought, Imagine the elevator was in a spinning spaceship of radius 'r' such that the top of the elevator was facing the center and the bottom of the elevator was facing radially outwards(and the base of the elevator was connected to the rim), Now if I was outside the space ship looking at the second mass from the outside we could find the equation of the second mass' motion!!!Physics is truly

[_John_Sean_Walker]

Thank U professor, for this wonderful problem. Again it was fun to wrestle with.

[blower]

Hello! Professor Walter Lewin. How are you?

[Potassium]

hi proffessor I have already solve the equivalence principles and I have the answer why inertial mass and gravitational mass the same
I am sure 100% my idea is correct

Where can I pass my article or my papers ? it’s big lot help if you can give an advice

I hope you will notice me ❤

Last September I have already solve the equality equivalence of inertial mass and gravitational mass

well that’s the happiest part of my life
I have been carrying my idea for 3 years now Iast September I have solve why inertial mass and gravitational mass the same

[akosbakonyi]

So basically we can think about gravity as being constantly accelerated upwards by the Earth. Now if a think about what Einstein said (you cannot distinguish between being in gravity or being accelerated in space with any experiment), if a I am in a test chamber and I feel the same acceleration in the same direction for long enough time, then I would know that it must be gravity, otherwise by now I would have had to exceed the speed of light by now. Where am I wrong?

[ashishkumarpemmaraju]

ik heb een vraag....Suppose our legs are rigidly fixed to a plank with clamps and the plank is freely falling under the force of gravity with the plank's plane perpendicular to the direction of motion and exactly at the time when the plank hits the ground the clamps are opened and we jump off the plank then what will be the impact force on our body due to collision of plank and ground(provided the plank doesn't rebound)????

[jatinbhatt]

Of course we can say the result will be the same if a planet or rocket move with constant velocity or it is stationary as both are inertial F.O.R. but accelerating frames are not inertial.

[alhassanmohamed]

Professor did you have a hair cut because i think so?? and you looks so nice

[bhandariakiadi]

In your 8.01 lecture on momentum you bombarded different combinations of balls as in a newtons cradle, like 5 balls against 3 balls etc. Please explain mathematically that what happened was what was supposed to happen i being just a high-school pass student could not do it on my own please help.

[suryamanohar]

Hii Professor
could you please you help me in solving this problem
A geostationary satellite X of orbit radius R, situated above a point P on the equator. Another lower orbit satellite Y of orbit radius 0.81R. At 7PM on Jan 1, Y is sighted directly above P. On which day again of Jan can Y be sighted directly above P between 7PM and 8PM?
P.S: I'm a high school student and I've already searched on the web for solutions and I didn't find any of them.If the solution is big or complicated then simply provide me some hints regarding my questions.
Thank you, Professor.
Take care.

[ahmedabdalrahiem]

what if someone just wants to stay in front of you in real sir watching you explaining physics !!.., i really want to attend one of your lectures <3
give a visit to Egypt, sir.we well be grateful

[quackduck]

bring your cleaning supplies everyone
we've got to clean up the mess from the bloodbath