5G10.55 - Magnetic Linear Accelerator - Gauss Rifle

Code Number:
Demo Title:
Magnetic Linear Accelerator - Gauss Rifle
Linear Acceleration due to Magnetic Attraction
Area of Study:
Electricity & Magnetism
Ball Bearings, Square Neodymium Magnets Attached to Ruler, Plastic Wedge Plate, 2 to 3 Foot Piece of Molding, and Ball Bearing Style Neodymium Magnets.

Arrange the ball bearings so that each magnet has two on the right hand side.  Slowly roll the loose ball bearing in from the left.  It will pick up speed due to magnetic attraction.  When it hits the first magnet it will dislodge a ball on the opposite side of the magnet.  This ball will pick up speed as it rolls into the next magnet and continue the reaction.  The last ball will be ejected from the apparatus at a velocity of several meters per second.

NOTE: The velocity of the exiting ball bearing may be significantly increased if that ball is about 1/2 the diameter of the ball bearing next to the magnet.

Place the ball bearing magnets on the molding in the same arrangement as above.  Roll a ball bearing into the first magnet and observe.  The velocity of the exiting bearing is not as great as in the above example mainly due to larger mass considerations.

NOTE: A larger velocity may be obtained if the magnets are taped to the molding, thus limiting the recoil that each stage experiences.

  • Leslie Atkins Elliott, André Bolliou, Hanna Irving, and Douglas Jackson, "Modeling Potential Energy of the Gaussian Gun", TPT, Vol. 57, #8, Nov. 2019, p. 520.
  • Sebastian Becker, Michael Thees, and Jochen Kuhn, "The Dynamics of the Magnetic Linear Accelerator Examined by Video Motion Analysis", TPT, Vol. 56, #7, Oct. 2018, p. 484.
  • Leslie J. Atkins, Craig Erstad, Paul Gudeman, Jacob McGowan, Kristin Mulhern, Kaitlyn Prader, Gregoria Rodriguez, Amy Showaker, and Adam Timmons, "Animating Energy: Stop-Motion Animation and Energy Tracking Representations", TPT, Vol. 52, #3, Mar. 2014, p. 152.
  • David Kagan, "Energy and Momentum in the Gauss Accelerator", TPT, Vol. 42, #1, Jan. 2004, p. 24.
  • James A. Rabchuk, "The Gauss Rifle and Magnetic Energy", TPT, Vol. 41, #3, Mar. 2003, p. 158.
  • Nathan Goodman, "Magnet Demo Attracts Pupils' Attention", Physics Education, Vol. 40, #4, July 2005, p. 314.
  • Borislaw Bilash II and David Maiullo, "Rocket Balls", A Demo a Day: A Year of Physics Demonstrations, p. 108.
  • Simon Quellen Field, "The Gauss Rifle: A Magnetic Linear Accelerator", Gonzo Gizmos, p. 29 - 34.
  • Jearl Walker, 1.42, "Chain Collisions", The Flying Circus of Physics, Ed. 2, p. 20.

Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.