Equivalence Principle

011 - Equivalence Principle

In this video Paul Andersen explains how inertial mass and gravitational mass are equivalent. He shows you too simple methods for calculated individual inertial mass and gravitational mass. Albert Einstein used this principle to build his general theory of relativity.

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Music Attribution
Title: String Theory
Artist: Herman Jolly

All of the images are licensed under creative commons and public domain licensing:

[beissan-]

What a great video! Really understood the concept. Thanks :)

[setarehsaremi]

When we are asking that is inertial mass is equal with the gravitational mass, does it mean that at the first place we doubt the gravity is a force? because if we say the gravity is a force, then by putting "mg" equal to" ma", the two masses should be equal, since the gravity acceleration affected on a mass is really don't understand why these two masses should not be the same????

[MichaelHarrisIreland]

I really appreciate this 'simple' explanation as I'm somewhat fascinated by this principle. Acceleration and gravity being equivalent, and then where it isn't also, to add to the mystery. That difference might hold a secret.

[eliphasphiri]

Eistein s analogue was not complete, the objects must also be accelerating if it is to stand in relation to Newton s law

[showdowmonrach]

The master of clearing concepts!!!..luv all ur videos!!!👌👌✌️✌️

[NexusEden]

You're awesome as usual - however I would have clarified that Acceleration is the change in velocity (Delta) and not the Velocity (which is constant). Often students get confused with that rocket example that it needs to be Accelerating at 9.8 m/s^2 not just traveling at that speed. Otherwise excellent as always. :)

[painpeace]

I'm fucked up with my brain....I need to rethink hole physics laws....

[Chelle_Vibes]

Something I don't quite understand is that gravity, as we experience it on earth, is an acceleration towards the center of a mass. Given that earth is (mostly) a sphere, if you dropped two objects, wouldn't they be accelerating with an ever so slight angle with respect to each other, given earths center is at a slightly different reference to the objects?

How would two objects dropped in a linearly accelerating non-inertial frame have that same angle? If they don't have the same angle could you how could the equivalence principal hold the two as the same?

[RadoslavFicko]

Then mass is dual because it is both gravitational and inertial.Just like a particle and a wave in quantum physics.

[haroonaverroes]

Einstein built his assumption: equivalence principle based on g in potential energy ! funny enough.
the interpretation of equivalence principle is wrong.

[warpedwhimsical]

In the method you used to measure the gravitational mass of the penny, is the mass of the ruler itself causing an error in the result?

[ThinkerMahmud]

Yes! That has been super helpful! Thanks

[phongthule]

Thank you so much for making it so easy and helping me with learning

[FischersVideoer]

Question: Does that mean that the first man to ever invent mass, he would use the gravitational mass technique, then he would pick some reference value and say "I'm going to give this cube a mass of 1kg" and then he used that reference mass to assign mass values to other objects?"

[Potassium]

hi I have already solve the equivalence principles and I have the answer why inertial mass and gravitational mass the same

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

[willfilmon]

I'm not totally sure that you wouldn't be able to tell which rocket your'e in at video's end. Gravity weakens over distance so I could possibly measure a stronger gravity on the floor as opposed to the ceiling and acceleration probably can't mimic that.

[everythingisalllies]

I don't see the point of Einstein's comparison of the mass of the guy standing on the earth and his mass being accelerated by a rocket. Big deal... this doesn't change or even suggest anything different than what Newton said so far, so where did Einstein go from this observation to a idea that was revolutionary?

[johnwythe]

The fact that they are both the same, could tell us something about the nature of mass. That both are caused by the same mechanism.

[treasurehunter]

So would an object with negative inertial mass automatically have negative gravitational mass?

[Justsayin]

Really, what is being proved is that mass must be proportional to itself. This must be the case or the equations would never work. That the force of gravity is the same as inertial force is not true though. It is true that they are involved with mass proportionally though in whatever way they are working in their own independent ways. Gravitational force acts on the entire mass of a body at every point even when at rest. The force experienced in free space under acceleration on a body acts entirely at the application point of the force and is transmitted through the structure of that body. This is not the same thing. As mentioned, all that is proved is that mass has equivalence to itself. If I drop a 1kg Apple and a 1 kg Orange of exactly the same dimensions they will both seem the same as each other in the way they interact with the world but I could not say that apple's and oranges are the same thing. Our equations predict outcomes but they are not necessary an explanation of what is causing them.