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Physics 12U - The Egg Launcher

  1. Mar 17, 2007 #1
    Alright, so we were just assigned our ISUs for grade 12 physics, and I'm a bit confused as to what is the best design for my project.

    We are to build a 'device' that launches an egg over a 1 metre tall 'fence' that is 2 metres away. The egg must then go through an 'open window' that is another 2 metres away, and then it must land in a 'fish tank'. The reason why I use quotations for some of these objects is because they may be replaced by other ones - such as the fish tank that may just be a cardboard box.

    The device does not have to move, although if it DOES it can move closer to the fence and launch from a closer distance. I don't know if this will help though.

    To make this more clear, here's a diagram:

    http://www.freewebs.com/bassmaster4/

    The window is 1 m tall by 0.5 m wide. The fish tank is about 0.75 m tall and 0.35 m in diameter. Keep in mind, the position of the fish tank can be anywhere from 0 to 1.5 metres from the window wall.

    The <b>maximum </b> dimensions I can have on my 'device' is 1 metre by 1 metre by 1 metre.

    Any suggestions?


    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Mar 17, 2007 #2

    turbo

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    Does the egg have to survive intact?
     
  4. Mar 17, 2007 #3
    No, it's a fake egg... probably rubber. It doesn't matter what velocity it hits the tank with.
     
  5. Mar 17, 2007 #4

    turbo

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    Then build it and they will come. Really, you can slap together a launcher with a spring-loaded piston with a cup on the end to hold the "egg". Just make sure that you can easily adjust it for elevation and for spring tension and you're all set. Now here is a question that I'd like you to answer. Using your diagram of the wall, window, box, etc, what is the trajectory most likely to give you an accurate repeatable delivery? If you can, draw an arc on your diagram and repost.
     
  6. Mar 17, 2007 #5
    The diagram isn't to scale. Should I make it to scale first and then draw an arc?
     
  7. Mar 17, 2007 #6

    turbo

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    Yes, please do. The path is short, so air resistance, etc is not going to be a big contributor, but it would be nice to see if you appreciate the ballistics involved to get the "egg" into the "tank".
     
  8. Mar 17, 2007 #7
    Okay, the diagram has been changed to be relatively to scale (close enough I think). Click on the same link on my first post.

    By the way, thanks for your help.
     
  9. Mar 17, 2007 #8
    Also, I CAN'T move the launcher with my own hands. Something automatic has to trigger the egg launch.
     
  10. Mar 17, 2007 #9

    turbo

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    OK, now draw the trajectory of the egg that will make it possible for you to land the egg in the tank. For now, assume that air resistance is not a factor. This is the key to the exercise and you will have to build enough adjustment into your launcher to achieve the proper trajectory.
     
  11. Mar 17, 2007 #10
    I think you may have missed my last post. I already drew the trajectory... check my diagram (use the same link that I have in the first post).
     
  12. Mar 17, 2007 #11

    turbo

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    The trajectory does not show up in the image that I see in my browser. If you can't get the image to appear, you can describe the trajectory if you want.
     
  13. Mar 17, 2007 #12
    Okay... umm... the trajectory is a parabola? Obviously we're dealing with projectile motion here.
     
  14. Mar 17, 2007 #13

    turbo

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    And how can you maximize the on-target "hits" for your egg? How does that arc fit the limitations of your wall and your window and the placement of your target box? Describe how that "egg" has to get to the target. You can do this with little thought - you already know what the approximate path needs to look like.
     
  15. Mar 17, 2007 #14
    The egg has to go over the fence, then through the window. So it first has to clear a 1 m fence. Now if my launcher is, say, 0.5 m, I need to launch the egg so that it clears the wall by at least 0.5 m. But I can't give you exact numbers... I need to draw a proper scale diagram and make some calculations, right? Like find the x and y components for velocity, displacement, etc?
     
  16. Mar 17, 2007 #15

    turbo

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    You are confusing engineering with physics. Build the launcher, make it work, then quantify its properties if necessary. This is an exercise in practical engineering - nothing more. If you can draw a path that the projectile must take, you can design a launcher that can make it happen. The physics is encapsulated in the trajectory of the projectile. Everything else is engineering. If you understand the trajectory that the projectile must take, you are left with a simple engineering project (make it so!).
     
  17. Mar 17, 2007 #16
    Okay, so if it's basically engineering how do you suggest I make it? How about a mouse-trap for a launcher, would that work? And we're also being marked on the construction (whether it easily breaks) so what kind of material should I use?
     
  18. Mar 17, 2007 #17

    turbo

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    You can use a mouse-trap with a stop (why would you want a stop?) or perhaps you could could use a different actuator. You should consider that the mass of the platform might hurt or help you.
     
  19. Mar 17, 2007 #18
    Why would the mass of the platform effect me? When you say platform you're referring to the base, right?

    I'm REALLY bad at anything to do with engineering.
     
  20. Mar 17, 2007 #19

    turbo

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    The mass of the platform may effect the accuracy of the delivery system. Can you figure out why?
     
  21. Mar 17, 2007 #20
    I have no clue... seeing as how the platform is a separate entity. If the launcher is attached to the platform, I still don't see how it'll effect anything.
     
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