> 120 divided by 5 = 24. Not bad! 24 mph is only a bit faster than the speed at which experienced parachutists land.
This is of course being a little silly, but it does get the physics wrong. Your energy is proportional to the square of your speed, so you have 25x more energy to dissipate at 120 mph, not 5x. Even if your five point landing was perfect, each of the five 'hits' is the equivalent of a landing at just under 60 mph, not 24.
My intuition rings false on this -- I don't think this is right. In a vacuum, ignoring the rocket equation (that is, assuming ejected reaction mass is negligible compared to projectile mass), the energy required to produce the 120 -> 96 mph change is the same as that required to go from 24 -> 0. This works out in conservation of energy because the ejected mass has kinetic energy of its own.
In the case of you landing, I don't think energy balance is the way to look at it; each of the collisions that slows you down will transfer some energy to the ground. In terms of force, the force is dependent only on the acceleration, so it comes down to how long each impact lasts. If each "bounce" or "thud" lasts the same amount of time (I don't know if this is realistic) then each one will transfer 1/5th of the force, as the article says.
Potential energy is linear with height. AKA it takes the same energy to climb from floor 1 to 2 as 2 to 3.
Gravity is 32 feet per second per second aka you gain speed over time. In a vacuum 0 to 32 feet per second takes 1 second, 32 to 64 feet per second takes 1 seconds, 64 to 96 takes 1 second etc.
However, in the first second you fall 16 feet. in the next second you fall 38 feet because you where falling at the start of that second. Thus, it takes more energy to increase your speed.
PS: What's confusing about rockets, is your fuel has momentum. So, when use it your consuming the energy it took to get that fuel up to speed with you. Further, at low speed most of the energy goes into the exhaust not the rocket.
The answer is that you gain velocity by shooting rocket fuel out the back. The energy that the fuel loses is proportional to the the square of the speed of the rocket as well, so everything works out fine. The mass of the rocket fuel is small, but it's not negligible, especially considering that kinetic energy is far more concerned with velocity than with mass.
The article is humor. Let's not get too technical on the math. Of course you're going to be a pancake if you hit the earth at 120mph, even if you find a way to split the damage 120 ways.
> “If you ever fall off the Sears Tower, just go real limp, because maybe you'll look like a dummy and people will try to catch you because, hey, free dummy.”
Jack Handey is an actual person, the writer of the one-liners GP refers to: https://en.wikipedia.org/wiki/Jack_Handey (I'm not sure if he recorded the voiceover performance or not). Al Franken is a different actual person who also worked on Saturday Night Live and who is now a US Senator.
> 120 divided by 5 = 24. Not bad! 24 mph is only a bit faster than the speed at which experienced parachutists land.
Better yet, just put your hands in front of you and land on all ten fingers. Then it's only 12mph. /s
In reality your entire body is moving at 120mph, so you can't divide the forces in this manner. This a PSI problem. Total inertia distributed over a given area. And the results are much less favorable.
As sfeng describes in another comment, the math isn't right, but the concept does make sense. It doesn't negate what you're saying either though; the 5 point landing is basically a way of distributing the force over as much area as possible. (You can't accomplish the same thing by just landing on your side, because the mass of your body isn't evenly distributed across the surface that would contact the ground.) It does manage to distribute the force over time a bit too, which is also beneficial, but a less significant effect.
Protip: Put your non-dominant hand over your dominant hand instead of locking your fingers together. That way if something falls on you, your dominant hand won't be crushed.
Excellent read. Just a few more pointers from personal experience. When over water, "pencil" your body, feet first, at the very last second. Molecules of atmosphere, which are your friend at 120mph, are not so much when they are of water.
I've never been on the offshore survival course where they teach you how to jump off an oil platform into the sea and survive, but allegedly they tell you to cover your mouth firmly with the palm of your hand and pinch your nostrils closed tight between your thumb and fingers. Apparently when you hit the cold water your natural reaction is to breath in. Also, you must prevent water being forced up your nostrils and damaging your brain etc.
I have been. You do get to practice that jump off of a moderately high diving board, I forget exactly how high it is. But it's legs together, feet pointed down, one arm with the hand over your face pinching your nose and the other held tight to your stomach. Nobody mentioned doing anything special on entering the water, besides the obvious of swimming to the surface after you stop.
I’ve also seen cliff divers saying to clench your buttocks as tightly as you can; apparently it helps keep your legs rigid so you don’t knee yourself in the face, and may reduce the likelihood of internal injury from impact to the perineal area.
Another key thing is to open your legs soon after entering the water to slow your decent. Don't stay in that pencil position or you're likely to go deeper than you really want to.
A similar tree saved my uncle's life when he fell (drunk, stoned?) off a cliff once twenty years or so back. He did get stabbed by one branch, but overall a better outcome than a straight 100-150' drop to the stony ground below.
Speed skiers go over 150mph, versus 120 for a flat-oriented free falling person. It's conceivable that orienting yourself to slide down a groomed black diamond ski run could be a winning strategy, too.
Maybe you should target a steep avalanche terrain with fresh snow. Not only you have a hell of a ride while falling down, you get to enjoy a ride in a snowy feather all the way down the valley! Don't forget to mount your GoPro while boarding!
Man, I wonder if we're going to end up seeing someone's free fall smartphone video someday. Not everyone is going to read this article and be prepared to survive like we now are, so what if they decide to use those couple of minutes falling to try to record a message to their loved ones? The audio would be blown out but I don't see why the camera wouldn't continue working. That would be quite disturbing to watch.
Except then you're stuck in freezing temperature, with what is probably totally inappropriate mountaineering gear and odds are you've got an avalanche to dig yourself out of.
Same with MotoGP riders. They basically slide and then they have gravel/sand catches around the turns they are most likely to fall off. Sometimes they tumble. It's not pretty but it does the job most of the time. But, it's also perpendicular. So if you're in a desert, aim for the top of a large sand dune, try to get your perpendicular velocity as high as possible.
Pretty much what you'd expect - massive injuries, sometimes death. Search Youtube for "speed skiing crash" for examples. Sometimes people get lucky and just slide to a stop, depends on how they fall.
Since we're quoting Doug Adams: “The Guide says there is an art to flying", said Ford, "or rather a knack. The knack lies in learning how to throw yourself at the ground and miss.”
Ouch. Nice move for Americans to fly in France where healthcare is affordable. If you did this in the US as a tourist you'd likely be broke for the rest of your life.
Make sure to go back to your home country as fast as possible, and then just ignore the bills. They'll have a very difficult time collecting on a debt in a foreign country. Don't come back to the US as a tourist after that.
This reminds me of college, where sometimes the police would come looking for students who were foreign nationals, because they had gotten credit cards and then racked up huge balances buying stuff, but didn't bother paying the bill. When the creditors tried to have them served, it turned out they had already graduated and left the country. Good luck getting some guy in Indonesia to pay off his US credit card balance. What were these creditors thinking?
A post-mortem from a base jumper? Those can't be common...
As someone who participates in a reasonably-dangerous / reasonably-uncommon hobby, that discussion really resonates with me. So much in there to contemplate.
Readit News
This is of course being a little silly, but it does get the physics wrong. Your energy is proportional to the square of your speed, so you have 25x more energy to dissipate at 120 mph, not 5x. Even if your five point landing was perfect, each of the five 'hits' is the equivalent of a landing at just under 60 mph, not 24.
In the case of you landing, I don't think energy balance is the way to look at it; each of the collisions that slows you down will transfer some energy to the ground. In terms of force, the force is dependent only on the acceleration, so it comes down to how long each impact lasts. If each "bounce" or "thud" lasts the same amount of time (I don't know if this is realistic) then each one will transfer 1/5th of the force, as the article says.
Potential energy is linear with height. AKA it takes the same energy to climb from floor 1 to 2 as 2 to 3.
Gravity is 32 feet per second per second aka you gain speed over time. In a vacuum 0 to 32 feet per second takes 1 second, 32 to 64 feet per second takes 1 seconds, 64 to 96 takes 1 second etc.
However, in the first second you fall 16 feet. in the next second you fall 38 feet because you where falling at the start of that second. Thus, it takes more energy to increase your speed.
PS: What's confusing about rockets, is your fuel has momentum. So, when use it your consuming the energy it took to get that fuel up to speed with you. Further, at low speed most of the energy goes into the exhaust not the rocket.
Say m=2 so we're just left looking at the v^2 terms:
120^2 - 96^2 >? 24^2 - 0^2
5184 >? 576
So yes, the KE difference between 120 and 96 is greater than the difference between 24 and 0.
> “If you ever fall off the Sears Tower, just go real limp, because maybe you'll look like a dummy and people will try to catch you because, hey, free dummy.”
[1] http://www.deepthoughtsbyjackhandey.com/
[2] https://en.wikipedia.org/wiki/Jack_Handey
http://ufpnews.com/window-washer-survives-11-story-fall-onto...
Better yet, just put your hands in front of you and land on all ten fingers. Then it's only 12mph. /s
In reality your entire body is moving at 120mph, so you can't divide the forces in this manner. This a PSI problem. Total inertia distributed over a given area. And the results are much less favorable.
Also the author didn't mention my favorite survivor Juliane Koepcke. https://en.m.wikipedia.org/wiki/Juliane_Koepcke
Basically cross your arms, legs and look forward
When I was child I used have fun by climbing to the top of conifers behind our house to sit on the highest branch and just slide down
Each successive tiered limb would catch the bend on the ones above and I would slide down perfectly fine
Man, I wonder if we're going to end up seeing someone's free fall smartphone video someday. Not everyone is going to read this article and be prepared to survive like we now are, so what if they decide to use those couple of minutes falling to try to record a message to their loved ones? The audio would be blown out but I don't see why the camera wouldn't continue working. That would be quite disturbing to watch.
As someone who has actually done that, tumbling is really bad. The titanium artifacts in my foot and leg are a permanent reminder of it.
Stick to plain sliding and trust your leathers.
Also interesting that having a towel could be incredibly useful in this situation.
http://topgunbase.ws/i-flew-my-wingsuit-into-trees-and-woke-...
This reminds me of college, where sometimes the police would come looking for students who were foreign nationals, because they had gotten credit cards and then racked up huge balances buying stuff, but didn't bother paying the bill. When the creditors tried to have them served, it turned out they had already graduated and left the country. Good luck getting some guy in Indonesia to pay off his US credit card balance. What were these creditors thinking?
As someone who participates in a reasonably-dangerous / reasonably-uncommon hobby, that discussion really resonates with me. So much in there to contemplate.
Thank you!
Graham Dickinson died in January.
There's a blog entry that addresses that aspect:
http://topgunbase.ws/experience_doesnt_mean_shit/
>> Inexperience kills our new pilots.
>> Complacency kills our high-time pilots.