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Homework Help: A newton's 3rd law project

  1. Feb 18, 2004 #1
    I'm just looking for feedback from anyone who can give me ideas to build a vehicle (perferably a car) that is powered by newtons' third law. its basically moving a car by recoil. any suggestions??

    im thinking of something like a simple car with a ballista attached on the top. Ballista shoot back and moves car forward. but im pretty sure there are better designs out there....

    the goal is try move the car as far as possible.

    Last edited: Feb 19, 2004
  2. jcsd
  3. Feb 20, 2004 #2

    Chi Meson

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    Almost anything will do. Rubber bands are always a good and easy "energy storage" device. A simple trigger would be a string that holds a stretched rubber band to a nail driven into the front of the cart. Use a match to burn the string (check w/ yr teacher about the match) and release the ballast.

    You want maximum momentum of the thrown back object; that is, maximum combiation of mass and speed. If you use an object that is too heavy, it will lose out on the speed and your car will recoil less. Try several sizes of ballast (washers in a film can works well, and the mass is easily adjustable). The more time you fiddle with it, the more fun it will be and the better your grade will be.
  4. Feb 23, 2004 #3
    I have a great idea!

    When I was in eighth grade I did a project on newton's third law. If you take a two-by-four and cut it to 8 in. then stick some wheels on it, and make a slingshot at one of the skinny ends with two nails and a rubber band. Then you put a nail at the opposite end of the board. You then tie a piece of string connecting the single nail to the rubber band, making sure the rubber band is tight. then take a small piece of wood and drill a hole in it. make sure the small piece of wood is tall enough to reach the rubber band. then put fishing weights down the hole in the small piece of wood.(If you varry the weights, then you can explain how the different weights effect how far the car travels). It is required that you burn the string in order to eliminate any unnessicary interferance from scisors.

    I hope this works, and i would be interested on how well you do. Glad to be of help!
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