Elevator free falling..

superjonahgo

If an elevator.. was free falling at its max speed. Would i be able to jump while im in the elevator?

Curious3141

The max speed bit is irrelevant, free fall is free fall.

Even though the normal reaction force is zero, it's still possible for you to launch yourself from the floor of the lift as long as it's within reach. Within the non-inertial frame of the falling lift, before you launch yourself, you are experiencing no force and you are stationary with respect to the lift floor. When you launch off, you are experiencing an upward force that accelerates you upwards relative to the floor and your velocity is upward away from the lift floor.

Considering things from an inertial perspective outside the lift, you and the lift are both falling with an acceleration of g directed downward. There is no reaction force exerted by the lift floor on you. When you launch off, you are exerting a downward force on the lift that is accompanied by an upward reaction force by the lift on you. This upward force lessens your net downward acceleration, so that you momentarily experience less than g downward. Note that your velocity is still downward from the inertial perspective outside the lift.

MathematicalPhysicist

i think that the answer is yes, but i also think that this is the case even before it reaches its max speed.
perhaps you mean, are you still weigthless in the elevator also at the max speed?
the maximum speed of the elevator i think is reached when it lands on the ground, and thus you'll not feel weightless.

i may be mistaken, so wait for others to answer you.

daniel_i_l

Standing inside a falling elevator is the same as standing in a spaceship in space. If you can get your feet close enough to the ground then you can jump.

Farsight

An orbiting shuttle is effectively a free-falling elevator. It's falling towards the earth, but it's also moving forward at 18000mph, so it falls "around" the curve of the earth and never gets any closer to the surface.

The conditions inside the shuttle are basically be the same as inside your falling lift. You'd be weightless, and could push off the walls and ceiling etc, do pirouettes in the air, and fool around with globules of water.

http://members.aol.com/petealway/orbit.html

russ_watters

You would not be able to tell the difference between an elevator at terminal velocity and an elevator that is stationary (until it hits the ground, of course...). You can jump exactly the same height in it in either case.

Art

Well not unless you dropped your pen. You then might wonder why it is floating in the air in front of you. And when you jumped the fact you don't land would be a dead giveaway.

russ_watters

No, Art. If the elevator is at its terminal velocity, as the op and I stated, it would not be accelerating and therefore nothing would seem different from if it was standing still (or moving at a constant velocity, supported by its cable). Only when it is accelerating (at the start of the fall) would you be weightless.

Art

The thread is entitled Free Falling Elevator. The second poster clarified that, it's terminal velocity is when it hits the ground at which time you're jam and won't be jumping anywhere.

Danger

Art, terminal velocity is the maximum speed that a given body will accelerate to in free fall. Given enough time or great enough height, that is reached well above ground level. The OP specified that the elevator is at its maximum speed, so that has been reached even though it's still falling.

Art

Okay - I read it the same as poster 2 that in this thought experiment other factors were discounted and so the elevator would continue to accelerate at g until it landed.

Danger

Understandable. I had to read it a couple of times myself to determine that.

russ_watters

The question is not well worded, so it isn't bad to deal with both cases. The first few posters assumed one case and I assumed the other.

ZapperZ

I think it is best to wait for the OP to come back and explain him/herself. I have a feeling that this is another case of "bad wording" with a misconception of "free fall" implying "maximum speed" of some kind.

Zz.

Curious3141

I agree. The OP's question was very badly written and shows more than a little confusion of the concepts.

Cyrus

The answer is yes, and no. I'll explain why.

(This is a very VERY poorly written problem.)

The elevator cable snaps, and you and the elevator go into free fall.

As you and the elevator fall, the elevator will fall FASTER than you do, because it weighs MORE than you do. Because the elevator falls faster, there is the possiblity that it looses contact with your feet.

case (1): The elevator separates from you before reaching terminal velocity. Here, you can jump *BEFORE* you separate from the floor. But if you dont, there's still hope!

The elevator will reach a faster terminal velocity than you do because it weighs more, as already mentioned. BUT, as the elevator nears the bottom, it is going to compress the column of air that was below the elevator. This net pressure force will retard the motion of the elevator.

IF it can slow the elevator down fast enough, you might be able to catch back up and remake contact with the floor (But perhaps a few split seconds before impact ).

But then again, if the elevator is high enough, it could maintain its higher terminal velocity for a long enough duration that the distance between you and the elevator becomes so great that the dampening caused by the cushion of air below the elevator occurs before you ever catch back up.

case (2): another possible case is that you never separate before reaching reaching terminal velocity with the elevator. This occurs if the elevator falls at a rate that is negligible as compared to your rate of descent. You can jump from the floor at *ANY* point along your fall.