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Throwing 1Kg the highest without electronics

  1. Aug 3, 2015 #1
    hello everyone.
    me and my mates as some fun over the school holidays are having a competition to see who can throw 1Kg the highest without the use of electronics due to an unfair advantage to those more well off etc.
    my first idea was a rail gun but as that requires electronics it is unable to be used.
    other conditions on the competition is that the device/machine has to be no taller than 2m and no wider then 1mX1m. i was thinking some sort of pully system where i can put in a lot of force on the one end and achieve massive acceleration on the other.

    just wanted to get any tips on my idea or any other better ideas before i get making.

    thanks.
     
  2. jcsd
  3. Aug 3, 2015 #2

    Andrew Mason

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    Is gunpowder permitted?

    AM
     
  4. Aug 3, 2015 #3
    maybe. but probably not. haha
     
  5. Aug 3, 2015 #4
    Single machine? Can't two things be used? Like a see-saw and a large mass to hit it on a side?
     
  6. Aug 3, 2015 #5

    berkeman

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  7. Aug 3, 2015 #6
  8. Aug 3, 2015 #7
    A catapult like device?
     
  9. Aug 3, 2015 #8

    berkeman

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    Scale it up to the largest you can within your groups rules. Read about what the compound feature gives in terms of benefits to the archer... :smile:
     
  10. Aug 3, 2015 #9

    berkeman

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    Also, you might want to use some sort of ratcheting mechanism to pull down the cable, more like you see with a large crossbow...
     
  11. Aug 3, 2015 #10

    berkeman

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    On second thought, if you do use mechanical advantage and a latching/ratcheting mechanism, that gets rid of the need for the compound mechanism. The compound bow's claim to fame is the "let-off" as the cable is drawn farther back.
     
  12. Aug 3, 2015 #11

    Baluncore

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    The 2m height restriction may restrict the time available for acceleration.
    Must some form of energy be converted to kinetic energy at the muzzle?
    Must the item be “thrown” or is it permitted to use aerodynamics such as a simple inertia or rubber powered helicopter?

    Have you considered practice ball throwers or skeet launchers?
    Potato guns can be powered by butane, acetylene, steam or compressed air.

    What shape and density is the 1kg mass?

    Does the projectile have to be heavier than air? Air has a density of approximately 1.225 kg/m3.
    A 1m3 bag of He might win the competition.

    Must the 1kg payload be inert or can it include the carcass, envelope or lifting gas?
     
  13. Aug 3, 2015 #12
    Haha :D
     
  14. Aug 3, 2015 #13
    Yes, and I guess Hydrogen is within the rules too - 4x more lift!
     
  15. Aug 3, 2015 #14

    DaveC426913

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    A rocket or firework would easily outdistance even the best ballistic device.
     
  16. Aug 3, 2015 #15

    Baluncore

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    Not quite 4x more lift. See; https://en.wikipedia.org/wiki/Lighter_than_air#Hydrogen_and_helium

    The problem with this challenge is really the interpretation of the question and the test conditions.
    How literally are the words to be taken?
    Is the 1 kg a total mass ignoring buoyancy, or is it a 1kg downward force weighed on scales?
     
  17. Aug 5, 2015 #16
    And what is the volume of the bag though? lower volume will make higher density, right?
     
  18. Aug 5, 2015 #17

    Baluncore

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    It depends on whether the 1kg mass includes the gas and bag or only a 1kg deadweight.

    Only if the bag has significant mass compared to the gas. Since the lifting gas is not under envelope pressure it's density will be dependent on temperature and atmospheric pressure.
     
  19. Aug 5, 2015 #18

    Baluncore

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    The density of dry air is 1.29 g/l, (unfortunately wet air is slightly less dense so take care on humid days).

    Hydrogen, H2 density is about 0.090 g/l.
    The difference is a buoyancy of 1.2 g/l.

    The 1kg deadweight and say 100g balloon envelope weigh a total of 1100g.
    So it will require a capacity of 1100. / 1.2 = 916.7 litre H2.

    Helium, He density is about 0.179 g/l so it will give a buoyancy of 1.111 g/l.
    It would require about 1100. / 1.111 = 990 litre of He capacity.

    Since both of those are less than the 2000 litres available to the challengers, it can be done with either H2 or He gas.
    A 1m diameter spherical balloon will have a volume of about 523.6 litre.
    Two of those should do the job and they will fit conveniently in the 1m x 1m x 2m size constraint.
     
  20. Aug 5, 2015 #19

    DaveC426913

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    You could also do it cheaper and easier with a hot air balloon or even a simple chinese lantern.

    (A chinese lantern - being little more than a tealight and a piece of paper, things you probably have lying around your living room - would be particularly irritating to competitors struggling with complicated ballistic devices.)
     
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