7D20.60 - Stellar Fusion - Nuclear Fusion Model

Code Number:
Demo Title:
Stellar Fusion - Nuclear Fusion Model
Area of Study:
Modern Physics
Nuclear Fusion Model, Air Track, and Two Cars of the Same Mass with Large Magnets.

Place the cylinders into the vertically held Plexiglas tube.  When the green ends are facing each other, the system is simulating two electrons approaching each other, and they are always repulsive, independent of distance.  When the orange ends are facing each other, the system is simulating two protons approaching each other.  They are repulsive at large distances, but at small distances the repulsive force goes to zero and they become strongly attractive.  This is the analogy of the electrostatic repulsion that dominates at large distances, and of the strong attractive component of the nuclear force responsible for the energy released in fusion (The above is excerpted from the Kashy and Johnson reference below).

Place one of the cars near the middle of the air track with the magnet on the car facing the oncoming car.  As you gently collide the cars they will repel each other without touching.  If you collide the cars at greater velocities the magnetic repulsion will be overcome and the cars will touch.

  • Christopher Sirola, "May the forces be with you!", TPT, Vol. 56, #2, Feb. 2018, p. 118.
  • Paul Hewitt, "Figuring Physics April 2017 Answer", TPT, Vol. 55, #5, May 2017, p. 317.
  • Paul Hewitt, "Figuring Physics", TPT, Vol. 35, #9, Dec. 1997, p. 539.
  • E. Kashy and D. A. Johnson, "A Model to Illustrate Forces in Nuclear Fusion", AJP, Vol. 62, #9, Sep. 1994, p. 804.
  • David C. Pace, William W. Heidbrink, Michael A. Van Zeeland, "Keeping Fusion Plasmas Hot", Physics Today, Vol. 68, #10, Oct. 2015, p. 34.
  • G. M. Staebler et al, "One Mystery of Magnetic Plasma Confinement Solved", Physics Today, Vol. 67, #7, July 2014, p. 17.
  • Robert Ehrlich, "Nuclear Fusion Simulation",  Why Toast Lands Jelly-Side Down, p. 180 - 181.
  • Curt Suplee, "The Four Forces", Everyday Science Explained, National Geographic, p. 76.

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.