This is not a 'joke' question. If you were in a lift/elevator and the cables broke..(more details)?

Question

If you were in a lift and the cables broke at the 5th floor and you managed to 'jump' inside the lift (elevator) a nano-second before it hit the bottom would you survive with no injuries because you were mid-aire for that nano-second while the base of the lift (elevator) hit the ground? It's a question that's bugged me for all time, serious answers only please.

Answer 1

Okay so if you are falling towards the ground the problem is that you are going to have a lot of speed when you hit the ground and that's not a good thing at all. It is true that you can use your legs to push yourself upwards. If you could push yourself upwards enough you could reduce your velocity towards the ground or even cancel it out! So the question is how much upwards velocity can you give yourself by jumping.

So a little background first. Say a slingshot fires a ball at 50 m/s. If you were falling straight down towards the ground at 40 m/s and you shot the ball straight up it would have a velocity of 10 m/s upwards. How did I get that? I got it because you can just add and subtract velocities like that if they are in the exact same direction (or exactly opposite direction). I walk left at 5m/s along the ground and throw a ball same way at 6m/s it is then going left at 5ms+6m/s. Or if I threw it right at 6m/s while walking left it would start with a velocity of (5m/s-6m/s) left which is -1m/s left (that's the exact same thing as 1m/s right).

You can figure out how much upwards velocity you can give yourself by jumping using this formula:

vf²=vi²+2ad

vf = final velocity, vi = initial velocity, a=acceleration, d=distance

Imagine you're standing on the ground while we think about this for a second and that you are great at jumping and you can jump 1 meter upwards. You start with some velocity vi from your jump and have 0 velocity when you hit the peak of your jump at 1 meter in the air.

0=vi²+2(9.8)(1)

vi=4.4m/s

So if you are a strong jumper you can give yourself an upwards velocity of 4.4m/s.

Now finally back to the elevator, if you and the elevator fell from a 5th floor at about 15m height you would be going down pretty quickly, almost 20m/s before you hit the ground.

Now if you could jump upwards JUST before hitting the ground you might at best get almost 4.4m/s of upwards velocity and you could subtract that from your downards velocity of 20m/s. That gives about 15m/s and that is a big problem to hit the ground at that speed.

Unfortunately you wouldn't even do that well because not all of the force you applied to jump upwards would go into accelerating you upwards. Some of it would go into pushing the elevator downwards even faster so you would gain even less upwards velocity.

The short answer is you could reduce your speed a little bit but not nearly enough to stop yourself from landing way too hard.

Answer 2

I'm not a phyics major so I couldn't give you the exact numbers but this is what i know:

Those 5 stories (or 60 feet I imagine) would have you picking up alot of speed and you would gain a lot of inertia (that keeps you going). So you are flying down really fast and so is the elevator or lift (if you're not a yank). If you jump, that means you are essentially only pushing the lift down faster, not projecting yourself upwards.

If the lift has enough mass that you could project yourself upwards, you would have to push yourself up fast enough to match the speed of your desent to actually no have interia forcing you down. So if you can jump up in the air at the rate of about 60 miles an hour, you would probably be okay. Other wise, you would be owned.

Basically instead of timing the jump, you should be saying your prayers

Answer 3

if it was a totally free fall you would need to jump hard enough to have reached the 5th floor from the floor with your jump, xcept that since the first part of your jump is way faster then it may not be the strength to jump 5 floors but less, and the elevator wont be falling at free fall velocity cuz there are frictions that slow it so your jump can be even less hard, a nanosec b4 is too late though, try jumping earlier but not too early or you will hit the roof. Anyway I dont think your elevator is going to fall unless somebody wants to kill you.

Answer 4

Mythbusters acually did this experiment not too long ago. Buster was at 20 stories high, and when they dropped the elevator, Buster was hooked up to a spring to make him jump right before the elevator hit the ground. The results were that Buster really got busted up. But maybe at 5 stories, you may still have a chance.

Answer 5

No. You have velocity relative to the cab and also relative to the ground.

Just before the cab hits the ground, the cab has velocity relative to the ground of -Vc (since it is approaching). You have velocity relative to the cab of Vy, but relative to the ground your velocity is Vy - Vc. You are still falling, but for the moment just a tad slower than the cab.

While you are in the air the cab's velocity suddenly becomes zero, but you accelerate downward from Vy - Vc to -Vc as you fall back to the floor of the cab.

(Not to put a damper on this cheerful scenario, but Otis' enabling patent in - I forget, 1875 or something like that - was for a safety brake, mounted on the cab, that relied on tension in the cable to hold it off. If the cable broke, the tension would be released, and the brake would clamp around the guide rods in the lift shaft and prevent the cab from dropping more than a couple of inches. :)

Answer 6

PLease visit the website for the TV show "Mythbusters" on the Discovery Channel.

They actually rigged a crash dummy to "jump up" right before a crashing elevator hit the ground. Tested the whole deal scientifically. HIgh speed cameras and examination of the debris showed the dummy would've been a fatality had he been alive to begin with.

In a free fall, you have nothing to push against to jump up. You continue to accelerate until you hit terminal velocity. When you hit, you hit. There is no sneaky way out of it. Sorry.

Answer 7

No you would not survive - after 5 floors (let's say 50 feet)

time = sqrt(2*h/g) = (2*50/32.2)^0.5 = 1.762 seconds

1.762 * 32.2 = 56.7 mph

you and the elevator are traveling at 56.7 mph. If you jump up at 56.7 mph you would only be pushing the elevator away from you at the same speed you are moving. If you jump at 2 x 56.7 or 113.4 mph, you would have to take into consideration both your mass and the mass of the elevator, but you still would not be standing still. Not only would push your mass up, but you would also push the mass of the elevator down. Do you think you can push off of the elevator faster than 56.7 mph? Think of it interms of a moving car going 56.7 mph, what do you think?

Answer 8

If you managed to jump at a speed equaling your rate of descent, and you didn't hit the top of the elevator, and the elevator did not flatten, and nothing exploded, I think so. Very small chance though.

Answer 9

I understand what you are saying, but you would still be traveling at the rate of fall!
Lifts have a brake system that comes on with centrifugal force if the elevator begins to fall anyway!

Answer 10

you are the terrific! (a area- of tickles for u). "She spent 20 minutes finding on the orange juice can by way of fact it reported: "focus..." Blondie grew to become into hypnotized. "one hundred% organic" clean, orange you? = )