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Launch a ping pong ball. A little help

  1. Mar 4, 2010 #1


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    Hello all,

    Basically we need to come up with a planar bistable mechanism that will launch a ping pong ball. Here's a quick image I made: http://freewebsite.0nyx.com/images/mech.html

    The club link is supposed to hit the ping pong ball and the goal is to make it go as horizontally far as possible.

    By bistable it means that the mechanism must have two positions with unstable equilibrium position of max. energy storage somewhere in between. The mechanism is triggered with a slight push to the club link.

    So how do I approach this problem. Say I know that the length between two pivots is 2 inch. And I'm supposed to figure out the dimensions of the links and what type of spring to use. If someone can throw some background info to this mechanism or some equations for energy storage of spring etc. will be helpful.

    Thank you.
  2. jcsd
  3. Mar 5, 2010 #2
    For my project I used a rat trap ballista (so called catapult) To get the energy Iwas suposed to use Mohr's circle because of the orientation of the spring. But you should be able to use the energy version of http://en.wikipedia.org/wiki/Hooke%27s_law" [Broken] law.
    The way I cheated my lecturer was to set the device up vertically and I proved the potential energy by the change in static height maintained by the spring for different weights hung off it. Hope this helps.
    Last edited by a moderator: May 4, 2017
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