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Urgent please help

  1. Sep 20, 2007 #1

    key

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    I really need help fast. I need to design a mechanism which has to be placed inside a can. The purpose of the mechanism is to knock the can over. I also have to have a 6 seconds delay before the can is to tip.
    I can use any kind of can
    thank you
     
    Last edited: Sep 20, 2007
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  3. Sep 20, 2007 #2

    berkeman

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    Staff: Mentor

    What are your initial thoughts? Is the only limitation that the mechanism fit in side the can? Any other limits on materials or technology? Are you actually going to build it, or just write up the plans?
     
  4. Sep 20, 2007 #3

    brewnog

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    Programmable electric shock collar for a gerbil?

    This sounds like homework. Do you have any ideas already key?
     
  5. Sep 20, 2007 #4

    key

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    no see the ideas i had were the same as others and only one person can use an idea
    there are no limits on technology
     
  6. Sep 20, 2007 #5

    berkeman

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    Okay, I have a good one, but I'm not sure they will allow it. Can you use a small firecracker? If not, maybe a baloon and a candle....
     
  7. Sep 20, 2007 #6

    berkeman

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    No, a baloon and a 6 second fuse....that would work, and be reasonably safe.
     
  8. Sep 20, 2007 #7

    key

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    i am sorry but is there anything that does not involve fire

    Also how would i set up the fuse and balloon
     
    Last edited: Sep 20, 2007
  9. Sep 20, 2007 #8

    berkeman

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    Sure. You're not allowed any fire, eh? Probably a smart move by the instructor.

    Okay, you can still use the baloon idea (Quiz Question -- what do you need to do inside the open-top can to turn the bursting baloon into a sideways directed air jet?). You just need to come up with a 6-second timer mechanism that pops the baloon when it expires. I can think of a couple ways of doing it, but will leave that for you to do. Tell us what you come up with.
     
  10. Sep 20, 2007 #9

    key

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    i am sorry but i really dont know please please help and the can top has to be closed
     
  11. Sep 20, 2007 #10

    berkeman

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    Well you didn't say that before. Please be precise -- we could have both saved a lot of time.

    So you need a moving mass inside, right? With a closed can, there would seem to be no other option. Translation and rotation would seem to be two options. Tell us how you could use rotation..... And tell us some of your ideas for how to time the 6 seconds. BTW, how are you supposed to initiate the start of this 6 second timer if the can is sealed up?
     
  12. Sep 20, 2007 #11

    key

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    sorry you can make holes inside the can or the lid for the trigger
     
    Last edited: Sep 20, 2007
  13. Sep 20, 2007 #12

    AlephZero

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    That's a mean question! If you think about conservation of momentum, some of the "obvious" answers probably won't work.

    Anyway, who said the can has to have an open top? Is there any rule that says you can't turn the can upside down and have an open base (i.e. start your device, put the can over it, and wait for 6 seconds...)

    (Edit: I posted that before I saw your post about "the can has to be closed")
     
    Last edited: Sep 20, 2007
  14. Sep 20, 2007 #13

    key

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    the can has to be upward you can not turn upside down
     
  15. Sep 20, 2007 #14

    berkeman

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    Well, there you go then. Rotating mass with an energy source, and a timer mechanism for the trigger. Sketch it up, get it approved, and start building!
     
  16. Sep 20, 2007 #15

    key

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    sorry but I still don't know what to do
     
  17. Sep 20, 2007 #16

    berkeman

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    You are not trying very hard. We do not give out answers here on the PF to homework and coursework questions. Those questions are normally supposed to go in the Homework Help forums, and you are required to show your work and efforts in order for us to be able to help you. Please review the PF rules if you haven't seen them already:

    https://www.physicsforums.com/showthread.php?t=5374

    I've allowed this question to stay here in the general technical forums, because questions about projects are allowed in the technical forums, although that is usually reserved for more advanced upper division projects.

    Now, we are not going to give you a design here. That is your job as a student to use what you are learning in the class, plus use some of your creativity, to come up with ideas and pick the best one and build and test it. We can give you some global ideas and things to think about, but we will NOT hand you a design.

    Now look at what I've posted as my latest hints, and start sketching. What is a simple way to store energy for a rotating mass? What would be some potential ways to time 6 seconds (without any fire as you say)? How could you make a mechanism to trigger the release of the stored energy as the timer expires?
     
  18. Sep 20, 2007 #17

    key

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    sorry but i am trying hard and like i said before all my ideas have been taken in my class so i can not use them
     
  19. Sep 20, 2007 #18

    berkeman

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    Please go ahead and post a list for us of your ideas so far that are taken.
     
  20. Sep 20, 2007 #19

    key

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    i figured it out thanks
     
  21. Sep 20, 2007 #20

    berkeman

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    Figured out how to build your project, or figured out how the PF works? :rolleyes:
     
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