Gauss Gun

Here’s a really cool experiment you can do at home, where you can build your own gauss gun (or gauss rifle)! This is basically a magnetic linear accelerator, but the balls don’t accelerate enough to actually hurt anyone.  Still, you can see how dramatically fast they can go.

To build the gauss gun, all you need are 9 ball bearings (we used 5/8 inch diameter) and two neodymium magnets, which you can find online. You need to be very careful with these magnets because they are quite strong.

materials for the gauss gun

The first thing you need to do is tape the magnets to the floor. We used space in between the tiles on a kitchen floor as our track. Start by taping one of the magnets down and sticking the balls to right side of the magnet.

ball setup for the gauss gun

Next, place the other magnet a few inches away and do the same. You should have 4-5 ball bearings attached to the magnets like in the picture below. You can experiment how the spacing between the magnets and number of balls affect the overall acceleration of the device.

completed gauss gun

To shoot the gauss gun, just roll a single ball bearing along the tile line into the left side of the left magnet. You’ll create a chain reaction and a ball will go shooting off the right side of the right magnet!

How does it work?

The gauss gun is a great way to understand kinetic energy and potential energy. You can think of energy as an ability to do work. You should notice that your magnets attract the ball bearings with a pretty strong force. When you pull a ball bearing away, you are doing work to pull against this magnetic force.  So, when a ball bearing rolls towards a magnet, the magnet does work on the ball bearing and speeds it up. In this way, potential energy is being turned into kinetic energy.

When the ball hits the magnet, this energy is again transferred. Some is used up by making sound and a little heat. But, most travels through the magnet and stack of balls to the last ball. Because this last ball is pretty far from the magnet, it is weakly attached and leaves with almost the same speed as the first ball that hit the magnet on the left.

So, the green ball on the right leaves at a pretty fast speed and is accelerated by the second magnet to go even faster. Even more energy is transferred through the second phase releasing the last ball at a pretty incredible speed.

Adding more stages would theoretically increase the speed even more!

6 Responses to “Gauss Gun”

  1. Mike December 9, 2012 at 12:24 am #

    What if you only have one ball on each side of the magnet do you get the same results? What if the balls are magnetic themselfs..What is the magnet is much stronger like have a pullforce of 500 lbs?.. I Really like this ..I think you gave the most detailed explanation i could find on the net.

    • Alex November 21, 2013 at 1:10 am #

      This experiment only works because of the presence of multiple balls at one end. If there was only a single ball, the magnet would pull on the ball, cancelling much of the kinetic energy. That is why multiple balls are needed. Also, it is not a rifle, as rifles have (duh) rifling, or circular grooves carved into the barrel to impart projectile spin.

  2. explorabox December 9, 2012 at 3:52 am #

    Thanks for your kind words! Putting just one ball on the other side will probably not work. The kinetic energy has to be transferred to a ball that is further from the magnet than the one hitting (that’s why we used 4 balls). A much stronger magnet has the potential to increase the kinetic energy transfer (faster ball). You should try it out!

  3. diane fish October 12, 2013 at 2:55 am #

    What I want to know is: One steel ball to one magnet – where does kinetic energy go? If it is transferred to magnet, then what.

    Now, one ball to one magnet with one ball on other side – kinetic energy transferred but is magnetic force too strong and that other ball will not detach? Or will it detach and roll back. If so, ummm, does kinetic energy turn back into magnetic potential energy. If they are all done moving, does that mean all kinetic energy is MPE again?

  4. diane fish October 12, 2013 at 2:55 am #

    I meant ball, restated below

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