Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: East on 21/04/2003 00:59:29
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Say an elevator breaks & the cab falls to the ground. If you jump up right before the cab makes contact with the ground(so you would be in the air when the elevator hits the ground), would you still land as hard as you would if you didn't jump at all?
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You would still splat even if you do jump up! When the lift is falling your body will have the same velocity. If you jump just before the lift crashes, the velocity that you jump up and then land will not match that of the lift so although you may reduce your falling speed, it will not be sufficient to save you from splatting!
Thats Economics...
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At the moment of your jump, if you add the velocity of the lift that it taking you downwards and the jumping, the velocity going downwards (say negative) and the velocity of you jumping upwards (say positive) will definitely not cancel out as the negative velocity is so much greater. You are just left wil a slightly lesser velocity taking you downwards. Which probably isn't lesser enough to stop you squishing .... if you watch an action-picture of a perso in the lift, you'll see them going downwards fast, then slightlyslower then squishing.
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my typing is awful please forgive me :p
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I love that word "squishing" - definitely onamato..whatever the word is. Onomatopoeia, that's it !
So I guess the only way to survive a lift in free fall, getting back to the original (rather good) question, would be to suspend yourself on some very strong elastic bands from the roof of the lift and wear a crash helmet so that the rebound didn't decapitate you ?!
I have heard though that it is impossible for a lift to free fall thanks to a cunning victorian invention that is added to all lifts and which shoves locking pins outwards into a thing like a ratchet stopping the lift, if ever the cable were to snap. Does anyone know the name of this gadget and even the inventor ? Am I right in what I say ?
Pat
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even tho all elevators have those mechanisms to stop falling, some still break and the thing to do is to lie flat on the ground, cos this reduces the amount of inertia your body builds up for impact, although you will still sustain injuries, your probably wont die as much, interesting true anecdote, had an old family friend who was in a falling freight elevator at sweet factory or summut, but they had a crate of chewing gum, and he sat on that when it fell, and he left completely free of injuries, cos it absorbed the impact.
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The inventor of that safety device is Elisha Graves Otis.
The "jumping at the last moment" technique of reducing injury in a falling lift requires that you have (at least)the leg muscles etc to jump up to the same floor that the lift fell from. If the lift is rather lightweight then you need even better muscles but the point is entirely academic.
Lying down on your back is probably the second best way to avoid death; not being in a falling lift is considerably better.
A lot more people are injured on stairs than in lifts.
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The best way to reduce your injury do to the high acceleration when you reach the bottom is to lay on your back but as you will be floating about in micro gravity (vomit comet style) it might be a little difficult to arrange.
Jumping may cause you injury to your head when you bang it on the roof but this will be trivial compared with what you will sustain when you reach the bottom
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The (other) fundamental problem with the 'jumping just before you hit' solution is.... knowing when you are about to hit!
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your probably wont die as much,
Can you only partially die, then? [???]
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Batroost,
I often wonder why glass floored elevators are not more popular for just this reason. Just think of it as a "Unique selling point"
Of course there is another point. The question asked in the title is not quite the same as in the first post.
Q Would I survive in a falling elevator?
A Yes, just as long as it kept falling...
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If you had a pile of cardboard boxes, you could lie on top of it.
Why not install air bags in the floors of all lifts - just in case?
Or have a deep hole at the bottom of the shaft, full of energy absorber?
Cost, dear boy. Humans are worth only so much, you know.
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I have never seen a news item of a lift falling out of control, it must be very rare why do we need to take more precautions against it happening? life has many worse dangers.
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If you had a pile of cardboard boxes, you could lie on top of it.
Why not install air bags in the floors of all lifts - just in case?
Or have a deep hole at the bottom of the shaft, full of energy absorber?
Cost, dear boy. Humans are worth only so much, you know.
Or if the shute curved. You would be able to survive any length of fall if there was a curve to fall into.
[diagram=254_0]
as long as it was long and shallow enough
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If you had a pile of cardboard boxes, you could lie on top of it.
Why not install air bags in the floors of all lifts - just in case?
Or have a deep hole at the bottom of the shaft, full of energy absorber?
Cost, dear boy. Humans are worth only so much, you know.
I think you can go too far in some safety aspects, what we have now is (possibly) the best safety for the cost effectiveness of the lift. When was the last time you heard of a lift failing to stop and someone actually dieing as a result?
BC, has already mentioned that we have Mr Otis to thank for his lift safety device. here is a pretty picture of his device, which he tested himself to a packed audience.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi154.photobucket.com%2Falbums%2Fs262%2Fpf0604%2Fotis_diagram.jpg&hash=5beed4c6e335037a80bb1ec7768edc22)
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In a falling lift you're fine. In a lift that's hitting the bottom you have a problem (sorry, couldn't resist..)
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An airbag in the floor of a lift would be great on the very few occasions when it went off just at the right time. On the larger number of occasions when it went off by accident it would launch you violently head first into the ceiling of the lift.
Oh, and Rosy I already couldn't resist making that joke earlier.
Many lifts now, in addition to the safety device drawn above (thanks for finding a picture Paul) have some sort of buffer at the bottom. The last lift I saw with this feature didn't have a cable so it couldn't use Mr Otis's idea.
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The easy way to put it is like this:- If you were travelling at two thousand miles per hour in an Aeroplane and you were the pilot then you saw a mountain was in your way and you had five seconds to do something. Would shoving your feet against the planes windsheild at the time of impact reduce your impact speed against the mountain? No it wouldn't, just have a five second smoke!!!
..maff
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In London before the electrical distribution of power got going power used to be distributed by pressurised water.
lifts used to have a long rod going deep into the ground that pushed the cabin up and down.
this system survived up until WWII when the distribution network was destroyed by bombing although it had long since become uneconomic and was only usefull for buildings of a modest height.
An example has been preserved in the South Kensington Science museum and provides an inherently safe ride
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Hydraulic lifts are still used today, not just in museums- the lift I refered to earlier (with no cable) was hydraulic.
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Since the lift is falling at the same speed as you are, you'd find it pretty hard to jump. Bending your knees won't bring your body any closer to the floor, but would probably cause your legs to lift off the floor. You simply couldn't bend down to jump.
If somehow you did manage to propel yourself upwards (maybe pushing on the railing on the side), you'd have to be strong enough to be able to fling yourself several stories off the ground (Imagine being able to push yourself off a railing and jumping 6 to 12 meters in the air). If you could do that, you'd probably be Superman, so you would merely fly out of the falling lift, race downward at the speed of light and stop the lift from falling to the ground. Even better, you'd orbit backwards around the earth -- causing time to go backwards -- and post a note on the lift the day before that it's out of order.
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Sadly I read only today of an accident with a lift where an unfortunate woman was cut in half shortly after giving birth !
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Sadly I read only today of an accident with a lift where an unfortunate woman was cut in half shortly after giving birth !
Weird.
Any details?
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Maybe if the earth started falling too?
Oh wait, it's already in a free fall.
Yep, there's the solution, just remember to follow the spin
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Yes but it would have to be a very narrow frame of factors, you use the same muscles to jump as to impact, only an impact take your brain time to react to , a jump would be a preemptive action, and i suppose you would be very narrowly horrifically injured rather than dead.
If a sudden accel3ration (ala relativity provided by the base of the elevatior shaft) kills you , a jump of equal acceleration would also kill you. If humans could jump with such force as to out jump the elevator humans would have enough strength to acc3lerate there pelvis through there abdomen/or survive the crash, alot like an elevator crash. Thus this ability was rooted out by the darwin process.
That is unless we could jump slowly and for along time defling gravitys pull, like jet packs. Then when the lift stops moving you will be under acceleretion just the same as standing on the lift floor. Or accelerate over a ten year period to the top of a lift and juust as the lift strikes the floor accelerate at the maximum acceleration the body can withstand and hope you dont hit the floor too hard.
And superman is always swooping to save falling people, at the speed of a bullet, catches them like the man of steel he is and he doesnt even pull an arm off !
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...
A lot more people are injured on stairs than in lifts.
What about death per incident ratio?
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your probably wont die as much,
Can you only partially die, then? [???]
Maybe the aftermath PTSD makes you dead inside?
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There is at least one recorded incident of a lift falling when a small aircraft crashed into the Empire state building I don't know if the Otis device was installed
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methinks that if one just jump good enough one might get into orbit. Be sure to adjust your trajectory though, and beware the roofs.
This theory I will name jumping frog disease :)
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methinks that if one just jump good enough one might get into orbit. Be sure to adjust your trajectory though, and beware the roofs.
This theory I will name jumping frog disease :)
I think that has already been accounted for :(
https://en.m.wikipedia.org/wiki/Jumping_Frenchmen_of_Maine