# If in a lift we can tell if acceleration is due to g or to a push

• B
does that affect the equivalence principle?

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Hello, Alba.
does that affect the equivalence principle?
Yes you can .
Thank you very much
Okay...
The earth radius from equator is 6378.1 km, let's call it r
https://en.wikipedia.org/wiki/Earth
or 6378.100m

This is what makes me irritated. I'm calculating 1.7 m against a 0.1 km rounding. But, I'll do it anyway...

##F = G \frac{M * \text{my weight} * kg }{r^2}##
...
##F = 9.80627 * N * \text{my weight}##
...
##a_{feet} = 9.80627##
I don't know if my calculation is correct.
Thanks for the attentions.
You feet will feel 9.80627m/s acceleration on earth and your head will feel 9.806264773m/s2
Because your head is farther from the centre of the gravity. But there's no such thing on elevator.

Okay, seriously. No!
That's the concept of Einstein Elevator. Light, everything works the same as on earth.
But not everything!
On earth there's a very-very little different.

But just ignore my number. See the answer of the staffs in my post.

Sincerely.

Hello, Alba.
Yes you can ..
The whole post is based on the assumption that your feet-head axis is parallel to the radius of the source, which must no necessarily be the case.
But the point is not the a on your head or feet, the issue is that, whatever the difference, you can always tell when the F (or a) is coming from a push/pull i.e. on the inertial mass and not on the gravitational mass.

If Einstein knew that, what is the purpose of the example? More in general, how can our subjective perception or objective measurement of a phenomenon influes the actual state of the world?

Ibix
does that affect the equivalence principle?
In a small enough region you cannot tell why you are in an accelerating frame. If the region is large enough that the non-uniform nature of the gravitational field is measurable that will give the game away, but the equivalence principle does not apply to such a large region.

Janus
Staff Emeritus