What if you jump while falling in an elivator?

Question

I have always wondered the logics behind it. If you elevator was crashing towards the ground with ou in it;

What if you jump at the last second and you are in the air as the collision occurs:

1. Was it wise to jump?

2. Will it save your life or better your chances?

3. What is the physics behind it?

Answer 1

This is a difficult question.

If you jump at exactly the right moment you will transfer some of your kinetic energy to the elevator itself and less energy in your body would mean less damage if the elevator didn't have a roof. However, because it does have a roof you might get whacked on the head when the elevator did reach bottom and assuming the elevator deformed on impact it would transfer some of its energy back to you in the form or a head injury which would be soon followed by two broken legs and several compressed if not broken vertebrae. Finally your internal organs would not stop instantly so heavy organs like your liver and spleen would likely try to tear free of there holdings and result in massive internal bleeding. Now if you stood still you would only save yourself the possible head injury but you would have more kinetic energy.

Contrast this with lying flat on the elevator floor where the force of impact is spread more evenly over your body. You still have maximum kinetic energy but perhaps a little better chance of living or perhaps just a little slower death.

Anyway here's the physics of jumping. Every action has an equal and opposite reaction. If you can jump up to a height of h meters above the ground you have a potential energy of m*g*h where m is your mass and g is the gravitational constant. If you do this just before the elevator reaches the bottom you transfer that much energy to the elevator by increasing its falling speed slightly and reducing yours according to 1/2 * m * v^2 = m*g*h where v is the reduction in your falling speed.

Answer 2

1. no difference.

2. no.

3. think of when you jump from the ground - how long does it keep you in the air? That's how long you've delayed the crash.

alternatively, think of how much force you applied when you jump from the ground. That's how much less impact you've managed.

Now, since the elevator is close to free fall (assuming all the breaks failed, and the air and the rail aren't providing much resistance) you could break an ankle or leg if the elevator fell 10 meters (10 yards). Much more than 10 meters means you'll very likely break legs and more.

With impacts like that, the jump at the end will not likely save you from injury or death.

Answer 3

Jumping does nothing for you in this situation. When you jump from the ground into the air, you ultimately land on the ground with a small downwards velocity. So jumping in the descending elevator would cause you to land with a downwards velocity slightly faster than that of the falling elevator. It doesn't matter whether or not you were on the elevator floor when it made contact; you still hit the ground at freefall velocity. On top of that, the entire elevator is still going to get crushed all around you, which is likely to cause you injury above and beyond whatever would be due purely to falling.

Answer 4

The elevator has a much much greater weight and mass than a human being does. If it were falling, it would be falling much faster than your body and you would technically already be in the air, so it would be impossible to jump as your feet wouldn't be pressed against the bottom.
Even if it were possible you're still pretty much screwed. If the elevator is plummeting to the ground as you suggest, then the impact will probably be so great that the elevator itself would be crushed once it hits the ground.

Answer 5

1. NO
2. No, technically, if you jump, the gravitation point will switch to the upper side of the elevator, and when it crashes, the velocity and the gravity returned to the ground, so you will fall down too, along with the crash.
Anyway, you'll be destroyed by fire (still) if you are standing in a falling elevator.

Answer 6

The inertia from the elevator is transferred to you and thus you jumping at the last possible second won't matter at all. If you're lucky enough not to have the roof come crashing down on you then you'll still most likely suffer two broken legs.

Answer 7

I can't really answer your questions, but I can tell you that Adam and Jamie on "Mythbusters" said it would not help save you from injury.

Answer 8

1. No
2.No
3. Something someone made up to see if some would do it

Answer 9

http://www.straightdope.com/classics/a1_205a.html

I remembered reading this several years ago and Googled it for you. Interesting stuff.