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The Gauss Gun

License: CC BY-NC 3.0

Gauss guns are fun ways to launch marbles and demonstrate a number of Physics principals. [Figure1]

Despite sounding scary, the Gauss gun can actually be a fun device to make at home. The homemade track is essentially a marble launcher and can only be considered anything near a gun in its much larger refined forms. The device works off of the principles of magnetism and conservation of momentum. The materials needed to make the experiment are a track (a ruler), somewhat powerful, but small magnets, and magnetic marbles which can be purchased for around $20. The magnets are spaced out along the track and aligned such that their magnetic fields all point in the same direction. One or two of the marbles should be stuck to the same side of each of the magnets. One marble should be put at the end of the track on the opposite side of the magnets and released to start a chain reaction of marble acceleration down the track until the final one is launched off. Watch this video to see how a Gauss gun is set up and how it works:

The aligned magnetic fields push on the marbles and accelerate them down the track. When a marble runs into a magnet, it's momentum is transferred through the magnet and into the next marble on the other side. What happens is that every marble accelerates a little but the speed keeps adding up resulting in a significant velocity of the marble that is released at the end. In small homemade tracks, this speed really isn't a concern. However, one must always be careful of their fingers when working with strong magnets.

Creative Applications:

  1. What happens when you use marbles that aren't magnetic?

  2. What differences do you see between using one and two marbles per magnet? What happens if you use more?

  3. Why don't the marbles accelerate without the initial push given by the collision of the previous marble with the magnet?

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