Equivalence principle to argue mass and weight are the same?

[Jimmy87]

Hi pf, I have recently watched a YouTube physics video from SixtySymbols channel which is a channel of short physics videos presented by professors of physics from Nottingham University. The video (pasted below) argues that because of inertial mass and gravitational mass being equivalent this provides an argument that mass and weight are the same thing? He ends the video by saying that if some smarty pants scientist tells you that mass and weight are different because weight is a force then you can tell them that fundamentally they are the same due to the equivalence principle. I really don't understand the connection. I have come across mass equivalence before and I understand what it is and understand his explanation of it in the video but what I don't understand is how this can be used to argue that mass and weight are the same? I was always taught by all my physics teachers that mass and weight are strictly different. For example, if you have a mass sitting far out from any gravitational field then it has no weight since the product of its mass and acceleration due to gravity is zero. However, it still definitely has mass so how can these two things ever be the same?

Link to video:

https://www.youtube.com/watch?v=QSIuTxnBuJk&list=UUvBqzzvUBLCs8Y7Axb-jZewMany thanks for any help!

 

[anorlunda]

For example, if you have a mass sitting far out from any gravitational field then it has no weight...

Congratulations, you answered your own question correctly.

 

[Jimmy87]

Congratulations, you answered your own question correctly.

But if I'm right then why does a professor of physics argue otherwise?

 

[PeroK]

His conclusion at the end of the video makes no sense to me either. For example: the mass of a bag of sugar is the same on the Earth and on the Moon, but the weight is different.

I don't follow his argument that the equivalence of inertial and gravitational mass leads to the equivalence of mass and weight.

 

[PJC01]

Hello,

The equivalence principle states that the effects of gravity are indistinguishable from the effects of acceleration. In other words, an object in a gravitational field experiences the same forces and accelerations as an object in an accelerating frame of reference. This principle was first proposed by Albert Einstein in his theory of general relativity.

The connection between the equivalence principle and the argument that mass and weight are the same lies in the fact that the mass of an object determines its response to both gravity and acceleration. In physics, mass is defined as the amount of matter in an object, and it is a fundamental property of matter. On the other hand, weight is the force exerted on an object due to gravity.

The key point here is that the equivalence principle states that the mass of an object is equivalent to its inertial mass and its gravitational mass. Inertial mass is a measure of an object's resistance to acceleration, while gravitational mass is a measure of the strength of its gravitational pull. This means that the mass of an object, which determines its response to acceleration, is also responsible for its response to gravity.

So, while it may seem like mass and weight are different concepts, they are actually closely related through the principle of equivalence. This principle allows us to understand that the mass of an object is what ultimately determines its weight, and therefore, they can be considered as the same thing.

I hope this helps to clarify the connection between the equivalence principle and the argument that mass and weight are the same. If you have any further questions, please do not hesitate to ask. Thank you.