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Fewest Broken Bones

11/28/2006 11:29 AM

I spent the weekend putting Christmas lights up on the our house. While standing near the top of my ladder, the following question presented itself:

If a person is standing 30 feet up on a 40 foot ladder, and the ladder decides to fall over, is it better to jump to the ground, or ride the ladder to the ground, or ride the ladder part-way down, and then jump?

And by "better" I mean "fewest broken bones".

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#1

Re: fewest broken bones

11/28/2006 12:14 PM

Great question!

I used to walk on the roof for gutter cleaning and so forth, without any sort of personal protective equipment. I've developed a great deal of safety training programs for industry, and have felt a bit hypocritical. So not too long ago, I bought a harness and installed a few tie-off points on my roof. I feel a bit safer. But I still clean the gutters on one end of the house from a ladder, and often have the same thoughts you had.

As a kid, I use to play around with climbing a completely unsupported ladder and riding it to the ground, jumping at the last instant. Noisy, hard on the ladder... but fun.

I feel certain that, given 10' of the ladder above you initially, and given the mass of your relatively large ladder, you could jump at some point just before hitting the ground, and land pretty safely. Your jump would be almost straight upward, aligned counter to your velocity vector at the correct instant, using the mass of the ladder to react against. A violent enough jump would then nearly or entirely cancel your downward velocity. I'd guess that an explosive jump upward at an altitude of about 4' would work.

Maybe we could take up a collection for medical expenses, and elect a "volunteer" to test the theory.

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#4
In reply to #1

Re: fewest broken bones

11/29/2006 12:30 AM

A recent episode of Myth Busters busted the "jump right before the elevator hits" myth. Apparently you can only jump upward, from the significant mass of the elevator car or the ground at about ~3mph. With the elevator doing close to 50mph this is not a big help. I would guess that the only thing that will save you in the ladder situation is that you aren't falling very long. Fall for one second and you are going ~21.8mph. Having jumped once off a roof at about 12 feet I can say be careful to turn your legs outward slightly so you don't drive your knees into your face. I survived without breakage but it is rough on your joints.

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#12
In reply to #4

Re: fewest broken bones

11/29/2006 12:48 PM

Jumping just before the elevator hits is a bit different. The acceleration of a falling ladder is not the same as vertical free fall acceleration. Initially the rotational acceleration is is very slow, because the gravitational force vector and the motion vector are not aligned (and, in fact, should have been perpendicular just prior to the fall). Add the affect of the ladder scraping on the siding, and the rate at which you hit the ground can be much lower than if you'd jumped.

From 30 feet, if you jump you may never walk again, if you live. If you ride the ladder down, there are several possibilities that could work in your favor: siding friction, crashing through tree branches and shrubs, etc. I can imagine several situations in which your vertical component would be 5 feet per second (or even lower if it's your lucky day). An explosive jump straight up would help. Granted, this may be very very hard to do, given your state of mind and given that you are no longer pushing against the rung but the ladder sides.

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#2

Re: Fewest Broken Bones

11/28/2006 4:02 PM

If you jump, your acceleration is going to be that due to gravity. If you stay on the tipping ladder, you won't accelerate as fast - you're not moving straight down. So your terminal velocity won't be as high. However, you risk being injured by the ladder itself if it hits you or lands on you when you hit the ground. I'm guessing that's why most people's instinct would be to jump away from the ladder. Just my 2ยข.

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#3

Re: Fewest Broken Bones

11/29/2006 12:13 AM

Instead of trying it out and causing you harm, or anyone else for that matter I would check out a web-site that does interactive training on Ladders.

Such as www.always-ready.ca/course/ladder_safety.htm

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#5

Re: Fewest Broken Bones

11/29/2006 12:50 AM

I would get some training on Parachute Landing Falls and do as we say "a dynamite PLF"! Given that your training may fail you, you likely won't be too bad off unless you hit your head. Most military barracks are no more than three stories high for that reason - it isn't usually that bad of a fall. Of course, you see a lot of twisted ankles! Remember - "chin on chest!"

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#6

Re: Fewest Broken Bones

11/29/2006 1:13 AM

Of course if one is wearing his fall-arrest equipment that we all keep in our home closets then the short fall would be the least of our worries compared to hanging all by one's lonesome in the cold wind and possibly bruising the family jewels. The soon to be cold family jewels!

I know no one, including myself who keeps such equipment at home. So a human and a ladder, barring any differences in wind resistance will both fall at the speed of gravity. Neither will fall faster. I guess the idea about staying on the ladder is okay as long as the ladder does not cause more damage. Providing the ground is softer than the ladder, then the ground would absorb the impact of the human body somewhat and the impact may be spread over a larger area of the body compared to the situation where the ladder strikes the ground first, its impact is absorbed somewhat by the earth, and then the human body strikes the rails and rungs of the ladder, creating several severe pressure points. Wow, a long sentence.

From the world of modern motorcycling safety: In an unavoidable crash should one stay on the bike or try to leap free before impact? The current safety school of thought is to leap free to reduce the likelihood of being crushed by a flipping motorbike, pinched between it and other moving or stationary objects or being impaled by parts of the motorbike. Similar to the man on the ladder, both the motorbike and the human have an identical horizontal and gravitational speed as long as the human is on the motorbike. When thrown from a bike there is typically not much sliding, but rather a lot of rolling and tumbling. And the human may for just a brief moment travel a bit faster than the sliding and/or tumbling motorbike, but he will be going in a different direction than the motorbike.

Ing. Robert Forbus

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#10
In reply to #6

Re: Fewest Broken Bones

11/29/2006 12:27 PM

Actually, fall arrest equip is not a bad idea. I use it routinely, but rig it so that I cannot go over the edge when on the roof. Therefore, the tie-off points can be designed for 1000# rather the 5000# typical if a fall over an edge is to be restrained. No inertia reel is required. If I fall, I am never left hanging over the edge. (The actual forces involved, if one stays on the roof are quite small -- usually a small fraction of my weight rather than large multiples.) My harness, which is rated for actual fall arrest (5000#) was only about $39 bucks -- very good insurance, and even better, great peace of mind. I have several drops around my roof that would almost certainly be unsurvivable, if I fell. Working on a moderately steep roof without something to keep you from going over the edge is foolhardy, in my opinion, (and I am someone who's flown aerobatics, raced motorcycles at 150 mph, flown hangliders, etc.).

Actually, there is a huge difference in fall rate on and off the ladder. Assuming the ladder was setup correctly, it will not fall straight back, but rather to the side. It must rotate around its base to fall. Initially, the torque required to cause this rotation is very very slight. It is not until the ladder becomes nearly parallel to the ground that the torque achieves a value equal to the weight of the person times his original height (30 feet in this case) at which point downward acceleration will reach the same value as as if the person were simply accelerating with the full force of gravity. One reason talented clowns can climb and balance on ladders without any support at all has to do with this: the accelerations side to side are slight, if the angle remains close to vertical. Also, a ladder sliding along the surface of the house as it falls to the side will experience a fair amount of friction, further restraining its rotational acceleration. In the best of all worlds, it might even catch on something...

There is not agreement re motorcycles. Many racers use the motorcycle to take the abrasion. I've done this myself several times, and it works well. One of my best friends died when he parted company with his bike, only to have it land on him.

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#13
In reply to #6

Re: Fewest Broken Bones

11/29/2006 12:50 PM

I've been riding for about 15 years; nobody has ever advocated laying down the bike in a crash situation. When I say 'nobody' I mean nobody with significant riding experience, instructors at safety courses, or other informed sources. It seems the 'lay-your-bike-down-technique' is prevalent among new riders. Perhaps it is because they are still (understandibly) nervous about being on the bike to begin with. According to accident studies, there is very little time to react to an impending collision. Brakes are better at reducing the impact speed, then your safety gear will do a good job protecting you in most accidents... You are wearing armored jacket/pants, boots, good gloves, full face helmet, right?

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#15
In reply to #13

Re: Fewest Broken Bones

11/29/2006 1:14 PM

I don't think Ing. was advocating laying the bike down prior to an accident so much as what to do after it has already been laid down "for you" (e.g., by using the exhaust system where you should be using tires). Clearly, if you have wheels and brakes available, use them. Having already found yourself sliding along the ground, however, I am a strong advocate of putting the bike in a position to take the abuse: both abrasion during the slide, and upon impact as an energy absorber. Better to bend the bike than your body. The mass of the bike also tends to stabilize your ride somewhat, and can help to level rough ground. In racing, and running into tire walls, the bike can be a big asset in equalizing the huge mass advantage the tires have over you.

I'd love to think that my "safety gear will do a good job of protecting" me. However, that fact that bikes are 38 times more likely to kill you than a car suggests only that they help a little. Have fun, but ride carefully.

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#7

Re: Fewest Broken Bones

11/29/2006 2:46 AM

Easy! Turn around and climb down as fast as you can. (You will also land butt first, not skull first.)

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#14
In reply to #7

Re: Fewest Broken Bones

11/29/2006 12:53 PM

Although I might not recommed this, I know it can work, if planned. Clowns do this sort of thing, and I used to do it myself when I was a kid. I never turned aound, though, but climbed down facing forward. (We may be thinking of different situations, though: the ladder was falling away from me, by design.)

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#8

Re: Fewest Broken Bones

11/29/2006 3:34 AM

Don't even try this, take full precautions that the ladder cannot fail you in anyway whatsoever. Have someone hold the ladder.

I have a friend who is in rehab at this time after falling about 7 feet onto concrete and breaking two parts of his spine.... he cannot even stand for more than a couple of minutes....his job requires standing for long periods.....I mean the job he had BEFORE the accident. He will be in rehab till the middle of next year.....

He is lucky not to be in a wheelchair for the rest of his life!

He fell flat on his back, almost killing himself with a massive blow to the back of the head! Luckily a medical team were with him within 30 seconds (it was at a hockey match, he WAS a referee!!)

His life will now take a dramatic change.......at 50!!!

Play safe, not stupid!!

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#16
In reply to #8

Re: Fewest Broken Bones

11/29/2006 1:30 PM

I'd love to see houses routinely equipped with tie-off points. Tied off on my roof, I cannot fall off the egde. But when I work on a ladder , I don't have tie offs. If there were tie offs along the gutter, (for the ladder, not me) they could restrain the ladder so that it never gets moving fast enough to require the sort of heavy duty tie off points used in industry for fall arrest.

I think that having a friend at the base of the ladder is sometimes false security. Certainly, better than nothing, but with a huge weight on a long lever arm...

Perhaps your story is just the nudge I need to install tie-offs along my gutters.

Incidently, when I was looking for my harness, I went to Lowes to ask if they had harnesses for roofers and homeowners. The woman I spoke to said she wished they did -- her father died as a result of a fall off a ladder.

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#9

Re: Fewest Broken Bones

11/29/2006 11:00 AM

Personal Experience!

The ladder failed and folded at one of the articulating joints I fell about 15 feet. After three yrs of generally full time use of a cane I am now able to walk without it. I am still unable to climb stairs....Short story DO NOT JUMP! All physics aside the ladder took most of the impact with the earth. The trip down leaves one with a feeling of complete loss of control.

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Anonymous Poster
#11

Re: Fewest Broken Bones

11/29/2006 12:30 PM

A ladder is an inatimate object and is not capible of making any decision. If you place the ladder in a stable position and keep your weight centered (no leaning out) the likelyhood of a fall is greatly reduced.

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Anonymous Poster
#17

Re: Fewest Broken Bones

11/29/2006 3:07 PM

The total kinetic energy you will deal with is the same, only the direction varies.

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#18

Re: Fewest Broken Bones

11/29/2006 5:41 PM

You're screwed. Your impact energy is determined by your height. If you climb up before the ladder rotates significantly, you'll increase your potential energy and impact energy. If you climb down, your change in potential energy will accelerate the ladder's rotation and you'll still hit the ground with the same impact energy exchange. Best grab the string of lights. As they pull off, some of your fall energy will dissipate.

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Anonymous Poster
#19

Re: Fewest Broken Bones

12/01/2006 2:37 PM

Kind of reminds me of the Bugs Bunny cartoon where he is in an airplane diving towards the earth but saves himself by jumping out right before the plane hits the earth.... Pure Bunny crap....

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