The brakes in the elevator have stopped working.

[vetrox]

So I've just set off the weight limit alarm on the elevator at work and it got me thinking (thanks to ksp and the simple physics it has taught me)

A hypothetical situation arises in my brain

If the brakes were to stop working and the elevator plummeted to the bottom of the lift shaft. How would i save myself.

The old me would assume that jumping at just the right time (IE just before the elevator hits the ground) i would survive. (you know...if the elevetor didnt just implode on itself)

---------

Now, Am i right in thinking this is not true. For examples sake lets say the elevator decends at 100m/s. If i jump just before it hits the ground I would still die horribly. Lets say me jumping reduces my velocity by 10m/s. The elevator hits the ground at 100m/s and I, shortly after, then hit the ground at 90m/s Thus dying horribly.

Is my brain functioning correctly? Have i just given myself a new fear of elevators? (even though im fully aware of all the safety mechanisms in non hypothetical elevators)

Note: I am not taking into acount terminal veloceties of myself or the elevator. Or anything else that probably should be included. I'm just trying to keep it as simple as possible

Edited January 3, 2014 by vetrox

[sal_vager]

You are right in thinking it isn't true, I think Phil Plait has posted about this amongst others, your legs cannot give you enough of a velocity change to prevent your imminent demise, you'd hit the ground at slightly less than the elevators velocity at impact.

At least no one would see you looking silly by jumping, you being a gooey mess and all that

[vetrox]

your legs cannot give you enough of a velocity change to prevent your imminent demise, you'd hit the ground at slightly less than the elevators velocity at impact.

Thanks, I thought so. I managed to work it out all on my own

Although the way you have phrased it is alot simpler than my entire post *doh*

ITs the same thought process that I used to have about jumping into a moving train.

If the train has and open dorr and you manage to jump through that door onto the train (from a stationary platform) That train will be moveing at say, 100km/60mph and you are doing 0mph/kmph. Its just like jumping onto a treadmill really, but less hilarious

Edited January 3, 2014 by vetrox

[sal_vager]

There's a lot of safety equipment in modern elevators, so don't worry about the brakes, they are more like air brakes on a lorry, and need power to disengage

[Awaras]

The Mythbusters busted that!

http://dsc.discovery.com/tv-shows/mythbusters/videos/elevator-of-death-minimyth.htm

[sal_vager]

That train will be moveing at say, 100km/60mph and you are doing 0mph/kmph. Its just like jumping onto a treadmill really, but less hilarious

Depends on your definition of humour I guess, some people would be in tears from laughing, until they see all the blood anyway

[Surefoot]

Your best chance would be standing on top of the elevator (on the roof) provided there is an access from inside the cabin, and that you can get up there quickly. Then try and use your clothes to grip the ascending cable (if it's still there) - NOT YOUR HANDS -. All that in the few fractions of seconds you'll have . On most elevators i have seen though there is no roof access from inside the cabin, and of course the ascending cable ends with the counterweight in many designs, that leaves very little time... Otherwise it's like Mythbusters demonstrated, whatever is in the cabin becomes goo.

[Raven.]

Even if you were to jump with enough power and change in velocity, you would still be killed from the debris. However, like someone has already mentioned, there are a lot of safety equipment in elevators. I believe that modern elevators have an arresting device that holds the elevator in place if the main cable was to somehow fail.

[Seret]

Actually you probably could jump fast enough to cancel your velocity, because the only way the lift could hit the bottom of the shaft was if it was going pretty slowly. One of the safety features is automatic brakes that engage if the lift is falling too quickly.

[Horn Brain]

If the elevator were travelling fast enough to kill you when it hit the ground, then you would probably kill yourself if you jumped fast enough to survive. Think about it. Same velocity change.

Also, the roof of the elevator would kill you.

[Skyler4856]

I have thought of amusement park rides that drop you from 100 stories high to 100 stories deep while decellerating slowly to simulate different gravity levels

[iamaphazael]

Seret is kind of correct, in that most elevators have a mechanical safety device on them that if the car starts moving too quickly, it applies a brake to the cable, slowing it down.

Now, assuming the cable has snapped, all possible safeties have failed, and the elevator is free-falling to the ground, your best bet would be to lie flat against the floor of the car, to maximize the surface area that the impact force will be distributed over, and thus reducing your injuries as much as possible

[ZetaX]

If the elevator were travelling fast enough to kill you when it hit the ground, then you would probably kill yourself if you jumped fast enough to survive. Think about it. Same velocity change.

The velocity change is irrelevant. Your velocity change by driving a car or flying in a plane is higher, yet you live. The simple reason for that is that not velocity but acceleration kills you. And jumping spreads that one out a bit.

By the same reason, a good way to reduce letality is to try to absorb as much energy with your legs or arms (maybe breaking them). I am not sure about the optimal positioning there, though.

[Horn Brain]

The velocity change is irrelevant. Your velocity change by driving a car or flying in a plane is higher, yet you live. The simple reason for that is that not velocity but acceleration kills you. And jumping spreads that one out a bit.

By the same reason, a good way to reduce letality is to try to absorb as much energy with your legs or arms (maybe breaking them). I am not sure about the optimal positioning there, though.

You have to perform the velocity change over a maximum of the length of your legs. You don't get to take all day. This would be equivalent to landing on your legs at the speed of your jump, i.e. hitting the ground without the elevator.

[maltesh]

You are right in thinking it isn't true, I think Phil Plait has posted about this amongst others, your legs cannot give you enough of a velocity change to prevent your imminent demise, you'd hit the ground at slightly less than the elevators velocity at impact.

At least no one would see you looking silly by jumping, you being a gooey mess and all that

You're also basically in freefall while the elevator's plummeting. So even if you have the Viking Space Magic Strength to shove off from the bottom of the elevator hard enough to kill your plummet, actually getting your feet onto the bottom of the elevator to do the jumping in the time you have before you hit is ma be a problem.

[lajoswinkler]

Yeah, if you'd be able to jump fast enough to null the speed of your falling body, that would break your bones, too. Jumping is useless.

The best thing would be to lie down facing upwards, and put something soft under your head like your hands. You will get great injuries (broken ribs and probably pierced lungs, concussion, fractured hip(s), pelvis to name a few) but your chances of immediate survival would be much greater than in the situation where you're standing up, kneeling, lying on your side, ... You'll still require immediate medical help to stay alive.

Also be sure to close your eyes and if you can, protect your face. Elevator will cave in and debris will rain on you.

Complete free fall is nearly impossible in modern elevators and is an extreme rare occurence and yes, it would look like the gravity is lost for a while. In the rare event of the car falling down with safety systems scraping and trying to slow it down, it's just plummeting with a rather slow terminal velocity where the car vibrates like mad and you break something on impact, or dislocate your ankles etc.

In most cases the fall is stopped by a whole bunch of passive systems. In order to really send the car down without any slowing down except air cushion, the car has to be sabotaged. It's not that easy.

[ZetaX]

You have to perform the velocity change over a maximum of the length of your legs. You don't get to take all day. This would be equivalent to landing on your legs at the speed of your jump, i.e. hitting the ground without the elevator.

Yeah, if you'd be able to jump fast enough to null the speed of your falling body, that would break your bones, too. Jumping is useless.

Both of this is wrong. Jumping spreads the time for the change of velocity/does a little bit of that earlier: id you jump right before impact, thus are slower than the elevator by a bit, then you impact the already crashed elevator floor with this slightly reduced speed, and therefore it has an effect.

It will not be enough in almost all cases, but I never claimed it does. Also, broken bones are really the least of cour concerns there.

[K^2]

ZetaX is kind of right. Jumping at the last moment effectively doubles the braking distance, which has potential to cut forces by as much as a half. That means that it increases the impact speed from which you can walk away without injuries by about 40%.

On the other hand, if we are talking about survival, you basically sacrifice your legs to the impact. There is no way to replicate the same thing with a jump. I mean, no matter how hard you jump, you won't be able to break your own legs. So contribution of the jump is absolutely minimal, and if we are talking about a lethal fall, jumping won't make enough of a difference.

[Horn Brain]

ZetaX is being a sore loser. Except in the very special circumstance where you're falling just a few percent faster than you could survive, this strategy will be about as effective as prayer. Not to mention it requires a roofless elevator and the ability to jump so fast that you dislocate and shatter all of your joints and bones in your legs, and probably break your back and neck.

[ZetaX]

Yeah, call people sore loosers for just giving you the physical facts, while never having claimed that this is viable in any way.

Also you seem to not have understood the statement itself at all, because my argument applies regardless how weak the jump is (but stronger jump -> less chance of dying); especially, the height of the elevator nor your strength matter for this to still somewhat have an effect, however weak it is.

It might help if you would be less of a dick to people that are just trying to put the facts right and explain what and why things happen. Nothing else was ever done by me in that posts, and a lot of the stuff you say was never claimed by me at all.

[Horn Brain]

For you, buddy.

[ZetaX]

Seriously, what is the point of your behaviour¿ (Apart from being mean)

If you or anyone else thinks I behaved wrongly, you can always point that (and how and why) out to me and I will not hold it against you. But so far your behaviour is completely uncalled for.

[Horn Brain]

Your answer is wrong. It's not a significant effect. Flapping your arms would be about as effective, because technically you could generate a bit of lift and your arms moving down would mean your torso would be moving up at some tiny speed which would (as you pointed out) lessen the impact. You could breath out through your nose really fast and fart to create upward thrust too!

The real measure is that it would be a much better use of your time to try and brace yourself in whatever position is most conducive to preserving your brain and internal organs than it would be to jump, flap your arms, rocket sneeze, or fart.

I'm sorry I trolled.

[Seret]

The velocity change is irrelevant. Your velocity change by driving a car or flying in a plane is higher, yet you live. The simple reason for that is that not velocity but acceleration kills you. And jumping spreads that one out a bit.

Specifically it's not the acceleration, but the rate of acceleration change. In things like ejection seats this is known as jolt force, and keeping it low is important for avoiding injury. The same acceleration will do more damage if it's applied quickly. When you jump you stop accelerating as soon as your feet leave the floor, so you've got a maximum distance of a squat to apply the acceleration. Whether that's a less severe jolt than the deceleration of the lift when it hits the shock absorber at the bottom of the shaft I couldn't say.

Edited January 4, 2014 by Seret