Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Stupid question

  1. Nov 26, 2007 #1
    Well at work today an arguement arose - me and one other person disagreed with about 12 others...and the thing is I can't seem to see how they'd be right.

    What I want to know is - could a man stop a helicopter taking off?

    The people I'm disagreeing with seem to think he could if he was strong enough to hold it down. I think that even if the man was strong enough to lift 1,000,000 helicopters above his head - no amount of strength makes him weigh more and the helicopter would just lift him off the ground. Unless the man's feet we attached to something on the ground surely there's no way he could stop the helicopter from taking off unless he had some sort of ability to make himself too heavy for the helicopter to lift.

    Silly I know, but I'd appreciate help - and maybe some explanation that I can give to people that would make them understand as anyway I explain it doesn't seem t oget through to them.

    Thanks.
     
    Last edited: Nov 26, 2007
  2. jcsd
  3. Nov 26, 2007 #2
    How DO you measure a person's strength - that is the question.

    If by "strength" you mean the ability to lift a helicopter above his/her head, then this has nothing to do with keeping one from taking off, as the first uses the earth as support.

    Realistically speaking, you are, indeed, correct. Unless we're talking about a toy helicopter ;). Or the man could hang on the something attached firmly to the ground. Although chances are the helicopter would rip him in two, regardless of his/her strength.

    --------
    Assaf
    Physically Incorrect
     
  4. Nov 26, 2007 #3

    DaveC426913

    User Avatar
    Gold Member

    I do not believe that any human is strong enough to hold on with enough strength to tear himself apart. I suppose, if taken to the extreme, his fingers/wrists would break, and then his hands would release.
     
  5. Nov 26, 2007 #4

    DaveC426913

    User Avatar
    Gold Member

    How exactly would this really strong man keep the helicopter down with any force greater than his own weight?

    Tell them they're reading too many Superman comics.

    You are correct, but I think you need to get clarification.
     
  6. Nov 26, 2007 #5

    stewartcs

    User Avatar
    Science Advisor

    Draw a free body diagram with all of the forces involved and show it to them.
     
  7. Nov 26, 2007 #6
    If they don't stipulate that the man be fastened to the ground, they are ludicrously mistaken.

    But even if they don't admit he is fastened, and yet still proceed as if he is i.e act as if his strength, rather then his weight, is what matters, then there is still a path to victory.

    Fight the fight they want to fight, that is, whether the tension in the mans flesh (his strength) is sufficient. How thick does a steel cable have to be to hold down a helicopter? If the answer is X thickness, then the question becomes "Is any man strong enough to snap a steel cable of X thickness?"
     
  8. Nov 26, 2007 #7
    It wasn't my intention to go into such detail, just to comment on the original possibility/impossibility :).

    --------
    Assaf
    Physically Incorrect
     
  9. Nov 26, 2007 #8
    That's what I said to them - The man's strength isn't even considered if he's been lifted vertically upwards - it's all about how much he weighs.

    This arguement actually came about from a scene in the TV show "Smallville" :)..

    A boy (Not Clark Kent) - apparently has super-human strength and stands on the ground, without any part of his body actually holding onto or attached to anything but the helicopter, he prevents the helicopter from going any higher than his head.

    The people at work seem to think that with his strength that would be possible physically - but physical strength souldn't come into the equasion.

    I noted it wasn't Clark Kent - as if human flight was possible I'd assume he'd be able to create a downward force (with the whole flying thing) greater than the upward force of the helicopter...but that's not really relevant to our arguement.

    Thanks for all the answers. :)

    Edit: I uploaded the clip to youtube if anyone is interested.
     
    Last edited: Nov 26, 2007
  10. Nov 26, 2007 #9

    DaveC426913

    User Avatar
    Gold Member

    Man I knew it. I knew it was Superman.


    Tell your friends that if they are learning their physics from sci-fi TV shows, it's a miracle they're still alive.
     
  11. Nov 26, 2007 #10

    russ_watters

    User Avatar

    Staff: Mentor

    And tell them, for the love of god, please do not watch "The Abyss"!

    Edit: you could also ask them if it is possible for someone sitting inside the helicopter to reach up, grab something on the ceiling, and pull the helicopter down. Then ask them the difference.
     
    Last edited: Nov 26, 2007
  12. Nov 27, 2007 #11
    I gave all the arguements listed here and most people accept them, but there's 2 left who are addoment that they're right and it's getting frustrating lol. :)

    Here's their arguement, they say that they've seen bodybuilders pull down (on a pulley system) on weights higher than their own body weight and lift them.

    They say that if this said strong man could create a downward force with just his arm greater than that of the force the helicopter is producing, his body weight wouldn't even come into the equasion.

    [​IMG]

    For arguement's sake we'll say the stong man weighs just 6lb (he's short), they say that if the man was incredibly strong he'd be able to create a downward force of say 11lb without any use of his body weight what so ever, just the muscles in his arm.

    I can see what they're getting at - but they're still wrong, right?

    How can I make them see?

    Thanks.
     
  13. Nov 27, 2007 #12

    stewartcs

    User Avatar
    Science Advisor

    This would only be true if the Ideal Mechanical Advantage (IMA) were greater than one (in this case). If the weight was heavier the IMA would have to be higher (or if the person weighed less).

    Additionally, most of the guys in the gym have their legs (knees) anchored while pulling down on really heavy weights. This allows them to pull heavier weights (heavier than their own) down.

    Same principles as described before, and yes your friends are still wrong.

    Your friends are on crack. Stop wasting your time with them. Find new friends. :rofl:
     
    Last edited: Nov 27, 2007
  14. Nov 27, 2007 #13

    Shooting Star

    User Avatar
    Homework Helper

    Search Guinness Records or Ripley's Believe it or not.

    A man used his teeth to bite a cable attached to a helicopter, which is pulling upward. Of course, the man is well strapped to the ground. The exact amount of tension in the cable is being is being shown on a spring balance. This violates no laws of anything whatsoever. Only shows that his teeth are very strongly attached to his body. I saw it on TV maybe six months or an year back. Maybe these friends are confused by a show of strength like this.

    Ask the two adamant friends to pull themselves up by their classical bootstraps.
     
  15. Nov 27, 2007 #14

    stewartcs

    User Avatar
    Science Advisor

    That's funny! :rofl:
     
  16. Nov 27, 2007 #15

    Mk

    User Avatar

    Right. And my skinny dentist's nurse can pluck my tooth out with her one arm that's obviously stronger than the x1000 horsepower engine of a helicopter.
     
  17. Nov 27, 2007 #16

    russ_watters

    User Avatar

    Staff: Mentor

    Quite a lot of people can do a lat pull of greater than their own weight. But the machine has a pad that pushes down on your thighs. Without that, you're doing chin-ups and you would lift yourself off the bench. Here's a pic:

    http://www.fullfitness.net/routines/machine_lateral_pulldown.html
    Ask for a demonstration from an in-shape coworker. Ask him to do a pull-up, then ask him to pull down harder than the pullup was without lifting himself off the ground. If the guy has ever done a pull-up before, the instructions won't even make sense to him!

    Or, take that diagram of yours and draw-in the additional forces. Make a free-body diagram of the situation and ask them to identify the force that holds you to the ground.

    Or, ask them to explain why it takes so many people to hold down a balloon in the Macy's Thanksgiving Parade (remember the parade balloon scene in Batman?)
     
    Last edited: Nov 27, 2007
  18. Nov 27, 2007 #17

    Shooting Star

    User Avatar
    Homework Helper

    ?? I posted a reply to MK. Where's it gone??
     
  19. Nov 27, 2007 #18

    Shooting Star

    User Avatar
    Homework Helper

    That’s right. It takes all kinds. People are different. Like the aforementioned two guys who believe that somebody can stop a helicopter from taking off without being strapped down to a fixed support.

    From the same TV programmes, I saw another guy pull a huge lorry some 100 ft or so, again using teeth. Another guy hangs from a support with the help of only hooks which have been pierced through his skin. One lady spent an hour with 50 odd cobras in a bathtub, was bitten 9-10 times, and came out smiling. This was for charity, somewhere in Indonesia, I believe.

    So many peculiar going-ons in the world…Look up these things I mentioned in the net.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Stupid question
  1. Very stupid question (Replies: 3)

  2. Stupid Power Question (Replies: 1)

Loading...