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Physics Slingshot Project Help

  1. Nov 2, 2007 #1
    Ok, a friend and I are trying to construct a somewhat large slingshot for a physics project. We want to be able to construct it and fire it with such accuracy that it can project a basketball into a hoop, some predetermined distance away.. Two questions: Is it possible to gain the accuracy and precision with a simple slingshot? How would I do it?

    I'm comfortable with the mathematics, but I'm a junior in high school and I'm not sure what I'm missing here.

    Thanks for the help!!!
  2. jcsd
  3. Nov 2, 2007 #2
    I think you'll need a very sturdy frame for the Y of the slingshot, and a very stable material for the elastic. Since the angles formed by both sides of the sling as they're drawn back is symmetric, it's the simple spring equation, isn't it? F = -kx. If there are any nonlinearities in this equation it will be hard to calculate in principal, but I doubt there will be. You know the mass of the basketball, so from there it's simple kinematics. This should give you a good approximation of the ball's flight (barring air resistence, random spin of the ball, etc) If the slingshot is sturdy enough it should be very easy to work out the smaller pertubations to the expected path by trial an error.

    I suggest you also arrange for the ability to change the angle of the slingshot with the floor, and be able to lock this into place. You also want a mechanism to draw the sling back, probably with a marked rule so the draw will be repeatable (keep in mind how far back the draw will have to be when you angle the Y to allow for the needed clearance). This mechanism should also be able to make a quick release in a repeatable way, which is more of an engineering problem then a physics one.

    Sounds like a fun project. You have to post a link to the YouTube video when you're done!
  4. Nov 2, 2007 #3
    Alright, thanks a lot! This helps. I will post a video link when it's all done, we're gonna tape it all.

    We plan on doing it outside on a hill, but we're taking into effect the wind. The only thing I'm worried about is how the ball is going to spin and if it will have a slight spin to one side or anything if it is misplaced in the sling pocket.
  5. Nov 3, 2007 #4


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    I'd recommend something similar to what is used to launch water balloons out windows. Use two or 4 strips of latex rubber, and a "cradle" to hold the basketball. You'll have to make some adjustments for temperature, but if the angle and draw distance are repeatable, then so should the results. A small amount of spin on a basketball won't affect it's trajectory over a reasonable distance.
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