Episode 120: Seesaw Saga

Air Date: May 20, 2009

A skydiver whose parachute fails to open can hit the high end of a playground seesaw, landing on his feet, and launch a child on the low end safely up to the roof of a 7-story building.

busted

In their first test, Adam and Jamie constructed a steel seesaw and placed a dummy on one end whose weight matched that of an average 6-year-old girl. To approximate the effect of a skydiver hitting the high end at terminal velocity, they calculated the proper combination of weight and height and dropped several water-filled barrels. The impact crushed the seesaw, ruptured the barrels, and launched the dummy to a height of 20 feet (6 m). Adam and Jamie went on to design and built a seesaw that could effectively deliver the energy of the falling skydiver to the girl without buckling.

The Build Team was brought in to further analyze the terminal velocity based on a specific type of skydiving suit and the diver’s body position; the determined it was 122 miles per hour (196 km/h). They also built a rig with bungee cords and guide wires that could accurately propel a dummy diver onto the target at the right speed. The child dummy was outfitted with “shock watch” stickers to measure the forces exerted on it. Three drops were carried out. The results:

1st drop: diver hit slightly off-center and burst on impact; girl flew 55 feet (17 m) up and 70 feet (21 m) laterally, but suffered enough force to kill her
2nd drop: sand-filled inner tube used for diver; girl hit the guide wires
3rd drop: girl flew 130 feet (40 m) up at an angle (equivalent of 200 feet/60 meters straight up), but experienced a g-force of 42 g which would cause serious injury even before she hit the ground

Based on the need for a super-strong seesaw and the injuries inflicted on the girl, the team declared the myth busted.

39 Comments

  1. Aaron Brant says:

    I’d like to start off the complaint by saying that I really do love the show and say that you all have pretty much an idyllic job.
    Now, I normally agree with your results, but have some problems with this one.

    1) The myth was that the girl was propelled up to the top of a seven story building and lived. One of the comments (I believe that Jamie made it) was that the girl fell to the ground far too hard to have survived. The laws of physics and trajectory state that when an object is propelled upward it’s vertical momentum is zero when it reaches the peak of it’s path. Therefore, the speed of the child anaglog at impact shouldn’t have even been a consideration. The only consideration should have been whether or not a skydiver could have propelled a girl on a seesaw that high. And that was proven conclusively.

    2) One of the other points brouht up during the myth wrap-up was that a skydiver could have propelled a small girl much higher than just a 7 story building, and that this story is a myth because it is greatly under-estimated. The problem with that is the fact that this part of the testing was greatly controlled and contrived. It is perfectly reasonable that only a portion of the sky-diver hit the higher end of the seesaw and only imparted a small portion of his kinetic energy to the seesaw. The only real results gained from this part of the experiment are that it is perfectly plausible that the sky-diver could have propelled the girl as high as the myth said.

    3) The myth was ultimately busted because the girl analog received far too many g-forces to have survived. If I remember correctly, the g-forces received by this girl were measured using shockwatches which a) measured the impact upon hitting the ground (which, again, would not have been a factor if the girl had landed on the building at the apex of her “flight”) and b) measured the g-forces of an impact that propelled her much higher than the myth required. Thus, basing the outcome of this myth on the results obtained from the shockwatches was a mistake because they registered a great deal of force that should not have been considered.

    In order to truly bust this myth the shockwatches should show that the g-forces required to propel a child high enough to reach the top of a seven story building, and those g-force alone, would be sufficient to kill a person of her size.

    • Enrico Martinez says:

      If the process was done correctly to propel the girl up to the 7th story building without sustaining any injury UPON the landing part procedure; WOULD the girl sustain any injury upon the immediate acceleration or force needed to propel her upwards WHEN SHE WAS ON the playground seesaw/catapult?

      • Ben says:

        Launch is greater acceleration than landing by a large margin. Definitely fatal. The summary doesn’t describe this very well.

  2. Andy says:

    I completely agree with Aaron Brant, especially point 2. You cannot bust a myth because the actual result is “better” than that in the myth. And mythbusters should have measured the g-force only for the height of the 7-story building for the purpose of testing the myth. Of course, just for fun (as they usually do) they can overdo, but do not use the results in the busting of the myth.

  3. Bill Yonescu says:

    Aaron Brant took the words right out of my mouth but said them much better. Since it’s a given that the landing of the child at the apex would not have seriously injured her, and since Mythbusters proved that the skydiver, under optimum conditions could have propelled the girl much hight than 7 stories, I would have to say that it’s very plausible that a miss-hit from the skydiver combined with a strong seesaw that partially broke and/or bent on impact, and absorbed just enough excess energy, could safely propel the child just to the top of the 7 story building.

  4. Russ P says:

    Well put. I was rather disappointed with this myth to be honest. They spent the entire episode making an over powerful system that wasn’t even required. They should not have built a super strong seesaw (it was hardly a seesaw anyways.) and run the myth as it was told, now to please viewers who want to see exciting results.

  5. Jon says:

    Hate to break it to ya but lets face facts.

    1) The Myth was simply that the girl was propelled upwards due to the skydiver hitting the seesaw. There was no details involved beyond the basic story so anyone griping that it wasn’t done correctly should shut up unless they personally witnessed such an event.

    2) The Mythbusters setup the myth in the most reliable, repeatable, and consistent way possible. To ask that they try to replicate every possible situation in order to prove the myth (no matter how unlikely it is to occur) they’d never finish the myth.

    3) The first test showed that the likely hood of a playground seesaw even being able to handle the impact of being hit by a skydiver is slim to none to begin with. They HAD to build the super strong unit just to get to the point of hitting that 70ft mark.

    4) The physics behind the myth itself can be calculated. I’m not a physics or engineering major (any other naysayers here that are?) but common sense would say that a skydiver hitting a seesaw and sending a 6yr old flying up 70 ft (nevermind the horizontal distance) would probably not leave the kid unscathed from the acceleration forces.

    • Micheal T. says:

      v= velocity (meters/second)
      Vo= initial velocity
      a= acceleration
      g= acceleration due to gravity (-9.8 m/s^2)
      dx = change in distance (distance of acceleration, or delta x)

      girl must travel apprx 21 meters in the y plane to reach 7 stories, assuming 10 ft (3.03M)/ story.

      V^2=Vo^2+2g dx

      -Vo^2=2(-9.8)21

      Vo=20.3 m/s

      Girl must have an initial velocity leaving the seesaw of 20.3 m/s in the y direction.
      assuming the see saw is 1.5m from ground to apex,

      V^2=Vo^2+2a dx

      20.3^2=2*a*1.5

      a=137m/s^2
      girl must accelerate an average 137m/s^2 in the y direction over the 1.5m distance.

      14g + 1g of gravity=
      15g

      humans have survived more than 45 g for short times, and 25 g up to 1.1 sec, which is more than enough time to accelerate the girl to the proper velocity.

      a 16th G could account for enough velocity in the x direction to transport the girl to the nearest building roof.

      F=Ma

      20kg*157m/s^2=3136N

      a force of 3136N (newtons) is required to acheive this acceleration.

      sky diver’s velocity upon hitting ground 705.6 m/s
      kinetic enerygy =
      705.6^2= 2*a*1.5
      165957.12m/s^2*90kg= 1.5×10^7N

      1.5×10^7 N is more than enough to impart the required force on the girl. the elacticity of the seesaw would drastically reduce the rate at which energy is transferred to the girl down to something closer to what is required, and the ground would absorb the rest of the energy.

      Assuming the seesaw was built properly to flex and deliver the required acceleration at a nearly constant rate (which is possible) the 16 Gs required are easily survivable by smaller children. This myth, according to the Physics and the math is Plausible.

  6. Eric says:

    Ok about this myth is that with jamies build seesaw was not like the average seesaw you would have in the playground..

    So for jamies seesaw, you guys got a total different reaction, then what the myth was to supposed to be about..

    So I would ask if you would try it again but as the normal seesaw that the little girl was on, to see that the effect of her outcome, that she surived.

    • MSpears says:

      They did try that. You must have missed it. A “normal” seesaw would just BEND under the impact. I’m sure SOMETHING would’ve happened to the girl, but flying 70 feet through the air? Nope.

    • Raju says:

      Three seconds is quite a long time, and the aricraft times were not too high either, according to the wikipedia article (about 30 seconds).I was quite skeptical of all the Hollywood movies depicting people jumping out of jet aricraft anyway. I remember seeing a program on discovery about a pilot who broke every blood vessel in his face by ejecting while supersonic.Another point which came to mind is that flight simulators might actually work (approximately). When a system is accelerated by a, the effective g forces will be $\\sqrt{a^2+g^2}$, and the simulator can give the actual direction, but not the magnitude by tilting the platform. I am not sure how effective it is really going to be as far as training goes, if your arm weighs 50 kg during a maneuver!

  7. Chris says:

    What was the name of the software used to Build the seesaw?

    The seesaw should have been flat so that the girl would of been propelled vertically…

  8. Devedander says:

    Sorry Jon, but you are way off and Aaron pretty much said what I would sans one point: The super sea saw did not replicate the direction a normal seesaw would accelerate a person. On a normal seesaw you start out with the bench angled away from the fulcrum and probably loose contact somewhere shortly after the midpoint of travel thus almost flying straight up. The super seesaw started flat to the ground and ended up angled significantly thus throwing the girl completely differntly than a real seesaw would.

    Now John

    1: Your argument is flawed. Yes the myth was not a specific case, but that actually is what makes you wrong. You cannot bust a general myth based on one specific example unless that example is the absolute optimum setup and still fails to achieve some part of the myth (ie if they could not launch the girl with a perfect hit super seesaw, then yes they could bust the myth, but in this case they did not do enough to bust the myth, just enough to prove that something more extreme than the claim could occur. Solid logic on your part? Busted.

    2: No one asks that they setup every possible situation, but if you are going to bust a myth you can only do so by showing some part of it is impossible, you cannot bust it by saying “under better conditions, even more extreme results occured, thus it’s not possible”. That would be like saying ” I proved you cannot win $100 by buying a lottery ticket. The test was I bought 500 lottery tickets and won $30,000. $30,000 is not $100 thus it is impossible to win $100 by buying only one lottery ticket. Aaron is correct when saying that if all the skydivers energy caused an exagerated effect, then it’s reasonable to say that some part of the skydivers energy would launch the girl less. In fact they showed exactly that when indeed only part of the skydiver hit the seesaw. So all the skydiver = too much energy, a small part = too little energy, thus there is some amount of the skydiver which would be about the right amount of energy. Your logic: Busted.

    3: They did not HAVE to build a super seesaw to reach 70feet… they DID build one and it well exceeded 70 feet. This means a lesser seesaw could have still made 70 feet. Also you will note they even mentioned in the show that sharp barrels do not replicate a body hitting very well. In the case of the barrel you have a lot of concentrated force in small areas. What they did cannot be used to bust the myth, it does not confirm the myth but if a super seesaw can launch the girl 130ft (note Jaime estimated 200 feet straight up) then it stands to reason a much lesser seesaw could handle the 70 foot launch. A normal seesaw? Maybe… that should have been the followup test. Your logic: Busted.

    4: While it seems highly likely that it would injure the girl to launch her that high, it is correct that they used shockwatches on (I believe) a 30 ft fall… If the girl really was launched at the right height (say about 75 feet) to clear the building, her shock on impact would have been equivalent of 5ft fall. Also while it’s likely that a launch like that would injure the girl, it’s hard to call… the seesaw may have been flexible absorbing some of the shock, a small girl doesn’t weigh much so remember that it’s not like launching you or I that high, and if you had to recieve such a launch, the seat of your butt would probably be one of the most resiliant places to do so.

    But yes, the launch is the hardest place to believe the myth, but other than that, you are completely off base. Sorry Jon, that’s just how it is.

  9. Damien says:

    As kid’s we used to do this ,the length and the structure (wood)was the key ,, the flex of the wood and the fact that we would push off just slightly to lessen the impacpt ,but we would still be able to do a somersault into all the elm tree leave’s we had raked into a pile , so i say if the girl had been on the up cycle , she could have beaten the rover to mar’s

  10. Dragonfyre says:

    It simply does not matter any of this…the myth is busted, because the girl would not have escaped unscathed. A normal seesaw wouldn’t have been able to withstand one drop, let alone the three they did.
    So let’s recap…seesaw would be destroyed, girl probably wouldn’t survive…that’s myth busted.

  11. livlivjr says:

    since the girl went 13 stories high she shouldve landed landed on a 13 storie building. if you fly 13 stories in the air and landed bac on the ground there is more g force and you would probably die but if u land on a 13 storie building u would probably live

  12. Dragonfyre says:

    livlivjr, that is possible, but highly unlikely. The girl experiences enough g-forces on the launch to injure her…landing on a hard surface would also cause some damage. In your scenario, she MIGHT live, but it’s likely to never happen.

  13. Dan says:

    Devedander, I like your rampage on johns logic, but even according to your own is flawed, because a skydiver landing feet first on a seesaw has an even greater concentration of force than those barrels, but thank you for taking time out of your day to rip on someone.

  14. Scott Johnston says:

    Having JUST seen this myth busting attempt for the first time I came to make a few complaints. I am however unsurprised to see that i’m not the first. Thank you Aaron Brant for being the first to point these out.

    The myth was that a skydiver at terminal velocity striking a seesaw feet-first would launch a 6-year-old girl onto a 7 story roof and she would live.

    I would first like to point out that the “Feet-First” aspect of this myth is only thrown in there for optimization of flight of the girl’s distance and helps define terminal velocity. If the skydiver lands feet-first then more of his body weight hits target at once at the highest possible speed, thus achieving maximum distance from the girl. If the “7 Story” distance can be resulted from another position, it shouldn’t invalidate the outcome. In short, the “feet-first” clause is more of a suggestion or guideline than a real requirement.

    This myth was busted for two reasons:
    1) the requirement of a super-strong seesaw
    2) the fatal injuries inflicted on the girl

    As Devedander expressed in point 3) the potential of the super-strong seesaw was WAY beyond that of the myth’s requirements. the super seesaw launched the dummy 13 stories, which Jamie said probably would have been 20 stories if it were straight up-and-down. The myth called for only 7 stories, which means that A) less force from the skydiver, either by less mass striking the target, or less mass in a different position with a slightly slower velocity would yield a smaller flight arc for the girl. B) a less efficient seesaw wouldn’t transfer the force as effectively, causing a smaller flight arc for the girl.

    The super seesaw was much more than required, thus if (and I do mean if) a regular seesaw could survive the impact, it would likely yield a lower result. They did do tests with a regular seesaw, however they were not impacted by a person, and they were hit head on.

    Dan complained that Devedander’s logic was flawed because the skydiver’s feet were more concentrated than the barrels; that the impact of a person would have been greater than or equal the impact of the barrels. This isn’t true. A person’s skin-and-bone make-up is more forgiving on impact than the barrels in question. In addition I have already discussed that the impact in the myth may not have been dead-on, or feet first. Until they can prove that it is impossible for a human analog to project a child analog 7 stories in the air without breaking a normal seesaw, they have no reason to label this myth as “busted”.
    –Inconclusive

    Secondly, As Aaron Brant stated, the damages to the child analog calculated by the shockwatches were from the force of being launched 20 stories (diagonally) in the air, and then falling 9 stories to the ground. These figures calculated that the child was dead. No Kidding. The myth was; did the child survive being launched just over 7 stories, and falling only a few feet. The measurements on the child analog are completely unusable as they don’t apply to the myth at all.
    –Very Much Inconclusive.

    In summary, The shockwatch data is unusable, and the super seesaw was nearly 3 times more effective then the myth required. If they can achieve 1/3 of that result without demolishing a regular seesaw, this myth is confirmed (pending the -likely- survival of the child). As it stands now there are no grounds to bust this myth yet! The jury’s still out!

    I suspect the only reason this myth was labeled as “busted” was because they ran out of time and had to call it, and they did so hastily.

  15. Chappy says:

    Correct me if I’m wrong but a ballistic trajectory has the same forces/acceleration acting on it at the start and end. [mgh=(mv^2)/2]
    That would therefore make the initial launch forces the same as the ground impact of the fall. So that means the girl would be seriously injured during the launch making this busted.

  16. Joshua says:

    chappy the initial launch forces are the same but there is nothing resisting them except the weight of the girl’s body,which is why she is launched into the air. The damage comes from the force impacting against the ground, not just her experiencing the forces. at the impact all of the forces are pushing her against the ground, whereas at launch there is the same amount of force, but it is pushing her up, against nothing but air and gravity, so she wouldn’t experience anywhere near the same amount of damage

  17. Scott Johnston says:

    It is still definitely possible that the force of the launch would injure/severely-injure/kill the girl, however as Joshua just said, there is far less resistance in the launch than in the landing due to the launch being against body weight and atmospheric resistance, where the landing is flesh, bone, and blood against pavement.

    The mythbusters did attempt to calculate any launch damage using shockwatches, however when the child analog fell 9 stories onto pavement, all of the shockwatches would have immediately triggered “dead”, thus making the attempted data gathering completely invalid. So we have no data as to whether or not she survived launch.

    Would a regular see-saw survive the impact?
    -Not likely, but possible. Needs further testing.
    Would a regular see-saw achieve a 7 story flight?
    -Possible. Needs further testing.
    Would the girl survive the initial launch.
    -Unknown. No Usable data. Needs further testing.
    Would the girl survive the landing at peak flight arc?
    -Probably, but unknown. Needs further testing.

    That’s 2 counts of probably, 1 count of probably not, 1 complete unknown, and 4 counts of “needs further testing”. How can you POSSIBLY get “busted” out of that?

  18. David gosselin says:

    in the myth the girl died because she did not land on the building

  19. David gosselin says:

    and when you throw a ball up in the air it stops for a split second and that is why she died

  20. Dead Eye says:

    The myth was busted when the average see saw was smashed into nothing ness from having a man fall on it at those speeds. Everything after the fact was what would we have to to to replicate it, which was build some sort of suepr see saw that now only exists in the M5 studios, everyone seems to over look these things and get hooked up on the math parts of myths. Every time I read these arguments, we skip right past the first part of the myth a girl on see saw, nos ” super ” see saw exists other than the one the guys built, and when the sky diver hit that see saw, his force destroyed the thing and only threw the girl far enough to give her scrapes and bruises, maybe a broken arm if she fell really bad.

  21. Logak says:

    My physics is a bit rusty, but from what I can gather, she’d endure close to 14 g’s from a launch that would get her 70 feet straight up in the air (and probably would need a little more since some lateral motion is a requirement). Less dangerous than 42 g’s, but could still potentially cause blackouts or whiplash. And again, I’m not sure that the force necessary for that kind of launch wouldn’t break an ordinary see-saw.

  22. Roy says:

    Was that thing they initially made a “standard seesaw”?

    Seemed like they could have made something intermediate between that and the “super seesaw”, but I can understand they ran out of time.

  23. Matt says:

    As far as the ‘normal’ seesaw being smashed to pieces, not all ‘normal’ seesaws are made of wood. Why not try the normal design made of something other than wood?

    • MSpears says:

      Actually, ‘normal’ seesaws haven’t been made out of wood in YEARS. Well, not the ones on playgrounds anyway, because we can’t have SPLINTERS in our children’s arses, can we?

      (*rolls eyes* Builds character, I say. LET them get splinters.) LOL! Sorry, that was the kind of thing my uncle might’ve said.

      Anyway, their ‘normal’ seesaw was made just like every other modern playground seesaw, out of metal.

  24. Matt says:

    Please disregard my comment, I had missed the first half of the show and just read the description of the episode. Lol

  25. scottmctony says:

    I do recall that the normal seesaw at the beginning was somewhat middle of the road. And of course the barrels gave it a disadvantage compared to a person. I think it’s actually likely that a high-end seesaw, impacted by the entire mass of a skydiver, could break just enough to reduce the force to something reasonably close to the myth. And I am almost certain that such force would only cause very minor injury in most cases.

  26. nicolas says:

    What was the name of the software used to Build the seesaw?

  27. Seneca says:

    I checked this website because I missed the last 10 minutes of the show and wanted to see if this was busted. I have to say the most entertaining part of all this is reading some of these posts…YGBSM Devedander et al, did y’all seriously spend hours composing posts about the merits of a mythical seesaw/skydiver test? Who cares?! It’s a freaking TV show! If you’re going to get yourself worked up about something, why not consider the national debt or the engineering of Japanese nuclear power plants.

    • Micheal T. says:

      they are engineered the same in Japan as they are here in the US.

  28. cortjezter says:

    i want to know why the girl was playing alone on a see-saw in the first place to even give a skydiver an open target to hit…

  29. Thiagozequim says:

    What is the name of the software that was used in the seesaw building simulation?

    • habbat says:

      SolidWorks

  30. bologna says:

    one thing i did see what was wrong that the seesaw was all the way down at the bottom if you sit on a seesaw you are higher off the floor due to your legs and that would give the angle of the girls flight when the skydiver hit it or if she was on at the bottom there would of been still a bit of a raise due to there always ( well what I have,use to play on at preschool a Tyre at the bottom to help with impact and also impact would help with the skydiver when he hits the other end of the seesaw

    i think they should just re test this with all the variables cause its just not right with Jamie colossal seesaw whatchamacallit it to a normal seesaw on a play ground that was a average one just my 2 cents

  31. Goner says:

    How realistic is it when they do not test with original materials?
    So have they undermined the whole test from the beginning.
    They exaggerate with weights, so it definitely fails.

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