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This one may be easier than cannibal logic

  1. May 11, 2005 #1
    The dilema of the bridge

    You are going into the jungle to play croquette with an old friend. on your way you come to a bridge. there is a sign that says weight capacity 185lbs.

    you think to your self i weigh 175lbs, my mallet weighs 5lbs, and my croquette balls weigh 2 lbs a piece [you have 3].

    the bridge is too long to throw them or roll them across. you are going to be late so you can't make more than one trip [meaning if you cross theres no going back]. There is no fraction and / or decimals of lbs involved and if you are even 1 lb over the capacity you will fall to your doom. What do you do to make it to the match on time? [note you must make it across with mallet and all 3 balls and your self]
    Last edited: May 11, 2005
  2. jcsd
  3. May 12, 2005 #2
    i cant believe you guys got my cannibal one in 15 minutes and no one knows this one lol.
  4. May 12, 2005 #3
    Juggle the balls as you walk across, that way you only have two balls in your possession at a time.
    Last edited: May 12, 2005
  5. May 12, 2005 #4
    Juggling won't work. When you toss a ball up, there is an equal and opposite reaction downward and the reaction force acts like weight on the bridge. Besides you've got that mallot.
  6. May 12, 2005 #5
    Are you 100% sure?
  7. May 12, 2005 #6


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    I'd count on the structural engineer having incorportated a factor of safety in his design, and cross the bridge on the assumption that an extra half kilo isn't going to make a difference...
  8. May 12, 2005 #7


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    Take of 1lb worth of clothes, go for a pee first, anything to reduce your weight a little.
  9. May 12, 2005 #8


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    I have three possible solutions:

    1) Leave your mallet behind. Come on, it's just a stick, and surely an "old friend" would be more than happy to let you borrow one during your turn.

    2) Remove a couple non-load bearing pieces of the bridge. After you have removed 1lb, then the maximum allowable load is 1lb higher.

    3) Tie some sort of string to your mallet and leave the mallet on one side. When you get to the other side, start pulling it in.

    ....thats the best i got.
  10. May 12, 2005 #9


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  11. May 12, 2005 #10
    juggleing was what i was looking for the mallet was useless info
  12. May 12, 2005 #11
    So then juggling isnt really the correct answer, according to Dave and jimmy?
  13. May 12, 2005 #12


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    Juggling?!?! I feel sorry for the guy who actually tries this...

    Personnaly, I'd use my acme hover-pod and fly there...
  14. May 12, 2005 #13
    I don't think it's a perfect answer, for I don't know how to juggle(or we can't presume atleast). Suppose if the guy starts juggling before stepping on the bridge we can avoid the reaction force equal to 6 lbs, if any. One ball is always in the air and second ball produces a 2 lb reaction or weight depending upon whether it is leaving your hand or in your hand.

    But juggling 2lb balls is what I fancy to see unless I am kind of Hercules.

    Further, even if the balls are made up of mercury, my rough calculation shows the diameter to be more than 2"(56mm).
  15. May 12, 2005 #14


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    Juggling does not work. Period.

    If it did, just imagine what we could do:

    We could make a juggling machine in the cargo hold of a 747, we could all fly our luggage to Italy for free. We could have the Juggletron keep 499 peices of luggage in the air and only be holding one at at any given time. 500 pieces of luggage and we only have to carry 40 pounds!

    Note that the juggling machine itself has a weight that is negligible. It only has to weigh enough to hold one piece of luggage (since it's only ever holding one piece at a time). It does not have to contend with inertia or momentum of the falling luggage. No matter how high you throw the luggage, as the force of the luggage coming down does not impart any force (and thus increased weight) to the juggling machine. If it were on a weigh scale, it would be juggling five hundred pieces of luggage and all the while never register more than 40 pounds.

    How many contradictions can you spot in the above Juggletron device?

    Juggling does not work.
  16. May 12, 2005 #15
    Well, you can't throw or roll them, but you have a mallet. Toss them into the air and whack them across.
  17. May 12, 2005 #16


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    This is actually a well-known physics riddle. It is equivalent to the 'birds in the truck' riddle.

    Scroll down to 'Juggling physics' and 'Fly away birdie' on this page

    P.S. If you're going to post a riddle, don't just make it up - you gotta at least make sure you know the answer!
  18. May 12, 2005 #17
    I like BicycleTree's answer though... if you're not good enough to do that, then you probably won't have fun playing croquette anyway. :biggrin:

    I guess you could find a sharp rock and cut the ropes on that side and make sure you hang on to the bridge so you can swing to the other side and then climb up....

    Or take your chance walking across and when it breaks make sure you're hanging onto the side that will end you up on the correct side.

    Another answer... this is the jungle right? Just use some of those Tarzan vines that must be lying around everywhere in the jungle... tie all your supplies up in your shirt and lower it to the bottom of the ravine and then carry the vine across (as long as the weight of the vine is less than all 4 other items you'll be fine). Then after you're on the other side you can pull the items back up using the vine.

    In reality there are a few things to try... for the riddle, the answer would be to juggle the balls (of course this wouldn't work as explained).
  19. May 12, 2005 #18
    I am 100% sure that the current model used by physicists to explain the world won't allow the juggling solution here. However, I am not 100% sure that the current model is correct. Is anyone?
  20. May 12, 2005 #19


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    I'm 99.9999% sure that it won't work. Unless there's a massive magnet floating overhead and the balls are metal...
  21. May 12, 2005 #20


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    Is your friend already there?
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