/sci/ - Science & Math

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Anonymous Sun Sep 16 23:20:00 2012 No.5064066 [Reply] [Original]

Sup /sci/
In physics class the prof was talking about freefall and he says if you're in an elevator that free falls then you die. But I was thinking on my own, and I'm basically the smartest person I know, and I did out the equations and got that you can survive by jumping at the last second. It's really surprising but it's actually true. But if you mistime by even a little you're fucked. How should I tell the professor? I wanna embarrass him because he's such a huge dick.

>>	Anonymous Sun Sep 16 23:25:14 2012 No.5064093 The roof of the elevator will crush you.

>>	Anonymous Sun Sep 16 23:30:44 2012 No.5064122 >>5064066 So instead of skydiving you should jump out standing on a big rock then jump off it just before it hits the ground.

>>	Anonymous Sun Sep 16 23:34:44 2012 No.5064133 where are you jumping to?

>>	Anonymous Sun Sep 16 23:39:14 2012 No.5064148 >>5064066 Well, this was done by Mythbusters. They proved it wrong. I didn't understand, however, one thing. What if I jump only 1 inch up and don't hit my head off the top. Will I survive?

Anonymous Sun Sep 16 23:39:14 2012 No.5064149

You can't jump when the lift is in total freefall as when it reaches terminal velocity you essentially have no weight (mass) and so would have nothing to push against. Your legs would feel "weak" or "heavy", you get this sensation slightly in lifts anyway.

I could give you a more detailed, longer explanation of how the lift has more mass than you and a higher terminal velocity but I can't be bothered.

>>	Anonymous Sun Sep 16 23:43:45 2012 No.5064163 Free fall minus the speed you can jump is still easily enough to kill you instantly...

>>	Anonymous Sun Sep 16 23:49:59 2012 No.5064179 Humans can survive a fall at their own terminal velocity. If you're in an elevator that free falls, you won't always die, but you are most likely to. Jumping is irrelevant, possible or not. >>5064148 >mythbusters as a source on sci

>>	Anonymous Sun Sep 16 23:50:45 2012 No.5064183 >>5064179 >Humans can survive a fall at their own terminal velocity. No they can't, not unless you land in a swimming pool of feathers... I've not seen anyone jump out of a plane and survive after hitting the ground without a parachute.

Anonymous Sun Sep 16 23:53:29 2012 No.5064195

>>5064183
I've never seen anyone jump out of a plane, so I guess that's your problem.

Oh, by the way-
http://today.msnbc.msn.com/id/17113222/ns/today/t/skydiving-miracle-man-falls-two-miles/#.UFaekI1lQ4
I
http://www.dailymail.co.uk/news/article-1256582/Woman-fell-3-000-feet-botched-parachute-jump-saved-m
iracle.html

>>	Anonymous Sun Sep 16 23:55:45 2012 No.5064207 > I'm basically thesmartestperson I know Work on your subtlety. 2/10.

>>	transfer student from /fit/ Sun Sep 16 23:57:45 2012 No.5064213 >>5064149 what you said is so stupid that i'd like you to give a longer detailed explanation of it so i can berate you

>>	transfer student from /fit/ Mon Sep 17 00:03:29 2012 No.5064229 also what i would do is straddle someone's back and ride them like a rodeo bull hopefully the snapping of his legs and landing on his meaty body would soften the impact enough to escape death

Anonymous Mon Sep 17 00:08:00 2012 No.5064236

You have to look at the bigger picture... You're falling at, give or take, 120mph.. Even if you jump at the last second, assuming you can generate enough force to relieve just half of the velocity, you're still hitting the floor at 60mph, more than enough to fuck you up badly. Just because you jump doesn't mean you're not falling at a smaller speed.

xor Mon Sep 17 00:10:30 2012 No.5064242

>>5064066

You'll only stop moving if your velocity is the normal force to the velocity of the elevator.

Since the elevator will be falling at an acceleration of 9.8 m/s, I doubt you could survive a 6-second fall because of your physical inability to exert an equal (preferably greater!) and opposite force to the final velocity of the elevator before impact.

Terminal velocity isn't that important here, although that would be another (minor) force to take place here.

Also, you're a conceited dumbass.
Two very bad traits.

>>	Anonymous Mon Sep 17 00:10:30 2012 No.5064243 >>5064236 This, to jump up and cancel out the force of you falling, youd have to jump as fast as or faster than the speed of which you are falling, Newton's Third Law, nigga

Anonymous Mon Sep 17 00:12:44 2012 No.5064245

Have you ever tried jumping up on a moving bus or airplane before? If you have, you would notice that you land exactly where you jumped, not further back from where you jumped like your intuition would like you to believe. That's because you're body is moving at the same velocity as the airplane/bus. I think you can see why you wouldn't survive jumping up on a freefalling elevator at the last second.

>>	Anonymous Mon Sep 17 00:14:44 2012 No.5064251 >>5064148 >What if I jump only 1 inch up and don't hit my head off the top. Will I survive? it doesn't matter. the elevator can have no ceiling and you'd most likely still die. you can't jump hard enough to counteract your downward force.

Anonymous Mon Sep 17 00:16:15 2012 No.5064253

>>5064213
But what he said is right, even though he didn't explain it well.
Your leg muscles can't apply a force to the floor of the elevator because they aren't in a position to do so. When you're in free fall you can't get into a squat position to get ready to jump, if you try to you'll just pull your legs towards your body and go into ball-mode.

Unless you were squatting on the floor when the elevator began to fall, it isn't possible to jump.
(and if you're from /fit/, you should understand muscle mechanics better than most people here, shame on you)

xor Mon Sep 17 00:16:15 2012 No.5064254

>>5064245

and you're moving with the bus because your perpendicular static friction constant is large enough between the material of the bus and your shoes, that you don't slide and instead feel perpendicular force at your feet.

The brain corrects this charge in intertia with liquids in the ear (somewhere?).

>>	Anonymous Mon Sep 17 00:19:59 2012 No.5064262 Oh dear god... >I'm basically the smartest person I know >you can survive by jumping at the last second This must be a troll. Please be a troll

>>	Anonymous Mon Sep 17 00:26:14 2012 No.5064287 What's up with all the people falling for this obvious troll?

>>	Anonymous Mon Sep 17 00:28:29 2012 No.5064297 >"I'm basically the smartest person I know" >Acting like they've proven something that everyone knows is wrong Troll detected

Anonymous Mon Sep 17 00:44:15 2012 No.5064343

Seriously, all of you saying it's wrong, do you even know the terminal velocity of an elevator? If the answer is no just leave and do some research, it's not as high as you think.
A healthy human would have enough strength to pull of the jump and survive due to the lower deceleration.

>>	Anonymous Mon Sep 17 00:54:15 2012 No.5064361 >>5064343 >due to the lower deceleration.

Anonymous Mon Sep 17 01:16:29 2012 No.5064389

>>5064343
say the fall is 5 seconds. the final speed would be around 120 mph. for an 80kg man this would be a kinetic energy of about115110.58 joules. assuming that same man can jump about 1.5 meters, then he can generate about 1176 joules in a jump. that leaves 113934.58 joules left of kinetic energy. in short, no, jumping does nothing.

>>	Anonymous Mon Sep 17 01:27:14 2012 No.5064403 irregardless unimportant http://www.cpwr.com/pdfs/pubs/research_pubs/elevatorconstructors2006.pdf

>>	Anonymous Mon Sep 17 01:30:15 2012 No.5064408 i think you'd be more likely to get hit by an elevator counterweight and die than from one falling in fact i'm not sure that people have died from the scenario described by OP within the last 20 years

>>	Anonymous Mon Sep 17 01:32:00 2012 No.5064417 >>5064389 Even if you did jump and decrease your downward velocity by some small amount, the potential energy you'd gain would turn right back into kinetic in the next second. Jumped does LITERALLY NOTHING.

>>	Anonymous Mon Sep 17 01:37:59 2012 No.5064426 >>5064183 It's actually happened before. Face first into a parking-lot, survived, and found out later she was pregnant. http://en.wikipedia.org/wiki/Shayna_Richardson

>>	Anonymous Mon Sep 17 01:41:59 2012 No.5064432 >>5064417 you didn't actually move upwards though, you simply decelerated. you don't gain any potential energy.

>>	Anonymous Mon Sep 17 01:42:44 2012 No.5064436 >>5064417 Nope. When you jump, you decrease your own kinetic energy and increase the elevator's. The elevator's kinetic energy is turned into heat, sound waves, the bending of metal, and possibly parts flying places, but it isn't returned to you.

>>	Anonymous Mon Sep 17 01:43:00 2012 No.5064437 you wouldn't be on the floor while you fell.

>>	Carl Mon Sep 17 01:46:14 2012 No.5064443 >>5064426 then you haven't looked hard enough. people have indeed survived falls from planes and 40+ story buildings.

>>	Anonymous Mon Sep 17 01:51:14 2012 No.5064456 >>5064343 So what's the terminal velocity anyway? I have no idea since there must be a lot of friction involved and I couldn't find it anywhere.

Anonymous Mon Sep 17 01:57:44 2012 No.5064471

>>5064456
it's a slightly negative velocity, since the counter-weight is heavier and would actually pull you up.
seriously though, this one will tell you if you can find all the variables. i'd guess aroung 100mph http://www.calctool.org/CALC/eng/aerospace/terminal

>>	Anonymous Mon Sep 17 02:35:29 2012 No.5064561 10/10 would play again

Anonymous Mon Sep 17 05:14:59 2012 No.5064941

Everybody knows the answer to this, so let's talk about the possibility of surviving the fall in any way.

What if you climb up through the ceiling of the elevator, and used some sort of clothing to grab onto one of the wires? Would the friction be too great?

>>	Anonymous Mon Sep 17 05:16:59 2012 No.5064946 >>5064941 how do you hold the cat? is it in a sling, or a knapsack?

>>	Anonymous Mon Sep 17 05:20:59 2012 No.5064961 >>5064946 Either way, but I guess it would rip apart if you hold it as a sling. And by the way, cat?

>>	Anonymous Mon Sep 17 06:01:00 2012 No.5065060 1

>>	Anonymous Mon Sep 17 06:17:15 2012 No.5065088 >>5064941 You just have to do a forward roll and you won't lose any hearts, unless you're falling down a bottomless pit.

>>	Anonymous Mon Sep 17 06:24:29 2012 No.5065112 >>5065088 Late ground-pounds will work as well. If possible, try and land in water or on an enemy.

>>	Anonymous Mon Sep 17 07:01:15 2012 No.5065145 only theoretical physicists assume elevators to be non-elastic. once the roof smashes their cranium, they start to think otherwise... but yeah, if you exchanged the air inside the elevator and made it more stable, who knows.

>>	Anonymous Mon Sep 17 07:18:14 2012 No.5065160 >>5064066 Wouldn't this have a similar effect to jumping on a train? as in you keep moving at the same speed as the train whilst in the air.

>>	Anonymous Mon Sep 17 07:27:45 2012 No.5065173 >>5065145 how are you going to jump through "stable" air?

>>	Anonymous Mon Sep 17 07:28:44 2012 No.5065175 >>5065160 I'm just going to give the benefit of the doubt and assume you didn't think that through before posting.

Anonymous Mon Sep 17 11:45:59 2012 No.5065636

The elevator being in freefall with you in it is just about the same situation as a floor segment being in freefall with you on it or you being in freefall by yourself. You collect a huge load of kinetic energy that you would have to cancel out with a single jump. Incidentally, that is, neglecting air resistance, the same energy you would need to jump from the elevator crash site back up to where the elevator started to fall. If you cant jump that strongly, you are out of luck.

>>	Anonymous Mon Sep 17 12:00:59 2012 No.5065683 Elevators cant freefall. They have compressed air underneath.

>>	Anonymous Mon Sep 17 12:01:59 2012 No.5065685 >>5065683 not if I attack a vacuum pump to the door in the basement

>>	Anonymous Mon Sep 17 12:02:14 2012 No.5065687 >>5065685 you will piss off the building super if you do that, believe me, cuz my brother tried.

>>	Anonymous Mon Sep 17 12:04:45 2012 No.5065694 >>5065685 But i knew you were going to do that, so i rigged,the basement door to close on your,hose.

>>	Anonymous Mon Sep 17 12:06:45 2012 No.5065702 >>5065694 ... is that a euphemism?

>>	Anonymous Mon Sep 17 12:56:14 2012 No.5065839 >the equations post them

>>	Anonymous Mon Sep 17 13:01:01 2012 No.5065846 >>5065702 Would you like it to be?

>>	Wolfram Book Guy Mon Sep 17 13:01:14 2012 No.5065847 >>5065839 EJumpthatsavesyou=EJumpthatpropelsyouuptheshaft

>>	Anonymous Mon Sep 17 13:15:29 2012 No.5065886 >>5064149 >you essentially have no weight (mass) >weight (mass) >weight = mass >/sci/

>>	Anonymous Mon Sep 17 13:15:59 2012 No.5065882 >>5064426 haha i bet she was raped while being passed out from the impact

>>	Anonymous Mon Sep 17 23:25:44 2012 No.5067566 this has been tested and works

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