For once, I’m siding with the engineers


I do trust the conservation of energy, and I do think evolved responses are often useful (but not always!), but most of all, I know that incompetent people can screw up badly. Recent example: leaving a loaded gun on a movie set. I’m not going to comfortably expect that somebody hung a massive object that could break my nose or worse did so correctly.

(Actually, I probably usually side with the engineers.)

Comments

  1. birgerjohansson says

    The engineers involved with the development of reliable ejection chairs for aircraft in the fifties are the origin to Murphy’s law: If anything can go wrong, it sooner or later will go wrong.
    Anyone associated with safety work of any kind should be aware of this.
    And since the science of prop guns are surprisingly complicated – at least if you want them to shoot flames and cycle realistically – the position of prop gun armourer should be like those Japanese fish chefs who handle a potentially poisonous fish;
    The apprentice need to work for the chef many years before being allowed near the fish.

  2. Ed Seedhouse says

    It doesn’t matter where or how they hang it, your nose is safe.

    If it’s held at your nose with the rope taught then you are safe where you stand after it’s released. So far as I can see the only failure mode is the rope breaking, but if it does the ball will just land on the ground.

    Any competent engineer should understand that and side with the physicist.

  3. whheydt says

    The mouse-over about the pre-med is also good.

    As for the reality of it.,..this engineer thinks, given where the ball is being held and the evident slack in the rope, that it will intersect the ground somewhere in the bottom of the swing.

  4. JoeBuddha says

    @birgerjohansson
    Those of us in QA love it when a coder just knocks something out without safeguards. It’s a target rich environment. Not to mention the fact that “that’ll never happen” is a lie. Lastly, if you make something completely fool proof, some ingenious fool will find a way to screw it up.

  5. says

    I read the other day that the Russian Roulette scene in Deer Hunter had a live round on set. De Niro requested a single live round in the revolver. The gun was checked three times on every take to insure that the live round wasn’t the in the next chamber.

  6. jacksprocket says

    As bcwx2 @1said, if it’s taut and given a push, it will swing back and slap your nose. Even if it’s not given a push, you’ve got to be confident your head stays in the same place. If it’s not taut, it could do a lot of things, and if it’s slack and given a push, well, being hit in the neck can be pretty uncomfortable too. The competent engineer builds safety margins into designs.

    Conspiracy goon: bowling balls don’t exist, if it hits you it doesn’t hurt, it’s all a plot by Big Gravity, crowdfunding facial plastic surgery….

  7. says

    And competent engineers test their stuff before subjecting innocent bystanders.
    That is what enables us to sleep soundly at night.

  8. davidc1 says

    Didn’t Richard Dawkins recreate Galileo’s famous experiment in Pisa Cathedral for one of his TV programmes ,I know he did for one of his xmas lectures .
    @7 In China Town ,both Jack and Roman made sure the fake knife used in the nose slitting scene was working properly .
    And i saw somewhere that in the film Don’t Look Now ,Donald Sutherland was lucky to survive ,because they used the wrong harness or rope or something in that scene when he is left hanging .

  9. Pierce R. Butler says

    Not having touched a bowling ball in decades, I expect they still have three holes, none of which penetrates all the way through.

    Which means the experimenter will need to kludge up the ball-rope connection with some off-balance improvisation probably involving superglue at best.

    Please allow me to observe well outside of, and at least 45° away from, the line of oscillation.

  10. brightmoon says

    On that one , I’ll go with the engineers too, even though I’ve got the biology degree.

  11. coragyps says

    A physics professor did that exact demo for us about 55 years ago in Fayetteville, Arkansas. He didn’t flinch, duck, or suffer a broken nose. He did impress the crap out of me, though!

  12. says

    @whheydt #15: Without knowing the material you can’t even guesstimate the strength of such a solution. Same goes for glue and screws.
    The best I can come up with is to bore through and secure with threaded rod, large washer and double nuts. It’s easy to calculate and you can guesstimate the bulk strength by dropping the ball from heights. A safety factor of 3 seems reasonable.

  13. naturalcynic says

    Fugu is definitely not potentially toxic. It contains tetrodotoxin in its liver and some other internal organs. The sushi chef has to know how to dismember it without contaminating the flesh.

  14. says

    @Ed Seedhouse#3: Your nose might be safe, but your teeth (or groin) won’t be. If it breaks before it’s highest point it will retain some horizontal momentum. So it can’t kill you, just make you wish you were dead.

  15. joestutter says

    If the rope brakes when it is just below your head the trajectory will change to the tangent of the arch and might actually hit you in the face

  16. birgerjohansson says

    Naturalcynic @ 18
    And that is why we should put fugu sushi chefs in charge of inspecting the people handling safety.
    If you have spent your career doing stuff that will kill people if you slack off, you will take this shit seriously.

  17. birgerjohansson says

    OT
    YES! New episode of God Awful Movies!
    (just giving other fans a heads-up)
    -Also, at Friendly Exmuslim they just explained the seven heavens BS in the koran.
    Also, it is the end of the Hindu Dinali festival. In one place in southern India they celebrate this by immersing themselves in cow dung. Because religion.

  18. Ed Seedhouse says

    Considering the path of the rope, the vast majority of the places the rope could fail are well away from your head. If you stand with your legs akimbo what is the ball going to hit except the ground or, in my case, possibly my vast expanse of my belly? If it breaks when it touches your head all the kinetic energy is gone and then only direction it will go is down. Your head would still be safe. Your gut might not be happy.

    Yeah, something could in theory be wrong. Well, airplanes fall out of the air every year but most people are willing to take the chance. An airplane is vastly more complicated than a straightforward pendulum.

  19. John Morales says

    Ed @3,

    It doesn’t matter where or how they hang it, your nose is safe.

    If it’s held at your nose with the rope taught then you are safe where you stand after it’s released.

    Well, me, I would stand back a half centimeter or so.
    Just in case I inadvertently lean forward ever so slightly.

    (Engineers surely know about safety margins much more so than physicists, who themselves at least grok error bars)

  20. leerudolph says

    (Engineers surely know about safety margins much more so than physicists, who themselves at least grok error bars)

    A physicist, a biologist, and an engineer walk into an error bar…

  21. says

    I side with the physicists because it doesn’t matter how you hang it. (Though I would still flinch because it’s an involuntary reaction.)

  22. says

    “If the rope brakes”

    The rope braking the ball is what we depend on.

    “when it is just below your head the trajectory will change to the tangent of the arch and might actually hit you in the face”

    I don’t know how you’re constructed, but my face is not below my head.

    Anyway … no, this cannot happen. The ball can certainly go further than its original position if the rope breaks, but only because gravity is acting on it, so the ball could hit you in the balls.

  23. says

    “Didn’t Richard Dawkins recreate Galileo’s famous experiment in Pisa Cathedral”

    Galileo never performed an experiment in Pisa Cathedral, nor from the leaning tower. He observed in his notebook that two balls tied together are heavier than either ball but can’t fall faster than the whole, and that likewise half a ball can’t fall more slowly than the whole ball, so Aristotle was wrong by logic, not just physics.

  24. says

    “The ball can certainly go further than its original position if the rope breaks, but only because gravity is acting on it, so the ball could hit you in the balls.”

    Oops … because the force of gravity only has a vertical component, the ball cannot in fact go further horizontally than the original starting point, which is the tip of your nose, so as long as you don’t have elephantiasis, your balls should be safe.

  25. Rob Grigjanis says

    Jim Balter @29:

    …because the force of gravity only has a vertical component, the ball cannot in fact go further horizontally than the original starting point

    Huh? If the rope breaks during the backswing (but not at the max height), it has a horizontal momentum component towards you, which will be largely conserved. So, depending where in the swing it breaks, it could hit you anywhere between your toes and somewhere on your upper body.

  26. davidc1 says

    @28 I thought he was in the cathedral ,and he was watching a lamp or something on the end of a long chain .

  27. Ice Swimmer says

    As an electrical engineer, I’d have one qualified person build the pendulum system and another qualified person to check it, before it can be energized. Then, because the rope is the only thing stopping the ball hitting the person, the person should wear protective gear, including safety shoes. Also, any static charge on the ball should be dissipated with suitable means.

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