Inertial Frames of Reference

So anyway..I am wondering why we go weightless in a free falling elevator
when the elevator leaves us behind.

If we are in the same reference frame, why does that elevator frame take
off....leaving us behind weightless?

"Mickman" wrote:

So anyway..I am wondering why we go weightless in a free falling elevator
when the elevator leaves us behind.

Elevators don't leave their occupants behind. If they did, elevators
would not be a good way to get from floor to floor.

Nor do you go weightless. You might if the elevator went into free
fall, but there are safety mechanisms that prevent elevators from
going into free fall.

If we are in the same reference frame, why does that elevator frame take
off....leaving us behind weightless?

You momentarily weigh less as the elevator accelerates downward, then
you momentarily weigh more as the elevator comes to a downward stop.
In between those two periods of acceleration, while the elevator has
constant velocity--i.e., zero acceleration--you weigh the same as you
do standing on the ground outside the building.
--
Dave

On Dec 14, 12:20 am, Dave Typinski wrote:

Nor do you go weightless. You might if the elevator went into free
fall, but there are safety mechanisms that prevent elevators from
going into free fall.

He wasn't talking about real-world Otis safety elevators. He was
talking about gedanken experiment elevators. So this won't help
answering his question.

John Savard

On Dec 13, 11:57 pm, "Mickman" wrote:
So anyway..I am wondering why we go weightless in a free falling elevator
when the elevator leaves us behind.

If we are in the same reference frame, why does that elevator frame take
off....leaving us behind weightless?

Oh, no. The elevator is weightless too.

I mean, it's not weightless from the outside, where we see it's
falling. But the elevator is freely falling, so it's in a reference
frame where it isn't sitting on anything that pushes against it to
hold it up.

The person in the elevator is judging his reference frame by the walls
of the elevator. So, like the elevator, he has no weight on his feet;
whatever pull gravity has on him, the elevator's downward movement
fully coresponds to.

John Savard

Quadibloc wrote:

On Dec 13, 11:57 pm, "Mickman" wrote:
So anyway..I am wondering why we go weightless in a free falling elevator
when the elevator leaves us behind.

If we are in the same reference frame why does that elevator frame take
off....leaving us behind weightless?

Oh, no. The elevator is weightless too.

I mean, it's not weightless from the outside, where we see it's
falling. But the elevator is freely falling, so it's in a reference
frame where it isn't sitting on anything that pushes against it to
hold it up.

The person in the elevator is judging his reference frame by the walls
of the elevator. So, like the elevator, he has no weight on his feet;
whatever pull gravity has on him, the elevator's downward movement
fully coresponds to.

Okay, thought experiment it is.

The elevator does not take off and leave the occupant behind. if it
did, then the occupant would eventually hit the top of the elevator,
at which time the occupant would no longer seem weightless. The top
of the elevator would be pushing down on the occupant.

The elevator takes off downward with the same acceleration that the
occupant takes off downward. The elevator's acceleration under the
force of gravity is the same is at its occupant's. Heavier objects do
not fall faster than lighter objects.

If the elevator and occupant accelerated at different rates, then yes,
the elevator and the occupant would not share a common interial frame
of reference with respect to each other. But they do, so they do.

One might imagine what happens while a Russian doll is in free fall
after being dropped. Ignoring the aerodynamic drag on the outer
piece, all the pieces are in free fall at exactly the same
acceleration.
--
Dave

Mickman wrote:

So anyway..I am wondering why we go weightless in a free falling elevator
when the elevator leaves us behind.


You arent weightless. You are still on the Earth last
time I looked. Maybe its your imagination? (and CAA
education!). Chck it out with Dick Bloviator at
CAA's famous "I know everthang" website.
http://cedar-astronomers.org/yahoo/Bloviation

Jerry




If we are in the same reference frame, why does that elevator frame take
off....leaving us behind weightless?