1D50.57 - Central Forces - Ball on Hoop

Code Number:
Demo Title:
Central Forces - Ball on Hoop
Forces Due To Circular Motion
Area of Study:
Ball on hoop chucked into hand drill.

Video Credit: Jonathan M. Sullivan-Wood.

Attach the apparatus to a short table rod with a parallel rod clamp.  Slowly rotate the apparatus until the ball swings upward.  As you slow the rotation rate, the ball will smoothly move down towards the starting point.  The ball will never go over the "equator".

NOTE:  To get the ball to move initially from its starting point will require a rotation rate greater than 1.6 revolutions per second and then the ball will jump up to fairly high level.  That is why it is usually better to start your explanation when the ball is at its highest level and then slow the rotation rate gradually until the ball is back at the rest point.

  • N. Gauthier, "Rotational Motion on a Hoop", TPT, Vol. 33, #5, May 1995, p. 262.
  • Said Shakerin, "Apparatus for Rotational Motion", TPT, Vol. 33, #3, Mar. 1995, p. 173.
  • Thomas E. Baker and Andreas Bill, "Jacobi Elliptic Functions and the Complete Solution to the Bead on the Hoop Problem", AJP, Vol. 80, #6, June 2012, p. 506. 
  • Richard V. Mancuso and Guy A. Schreiber, "An Improved Apparatus for Demonstrating First- and Second-Order Phase Transitions: Ball Bearings on a Rotating Hoop", AJP, Vol. 73, #4, Apr. 2005, p. 366.
  • Richard V. Mancuso, "A Working Mechanical Model for First- and Second-Order Phase Transitions and the Cusp Catastrophe", AJP, Vol. 68, #3, Mar. 2000, p. 271.
  • Richard J. Fitzgerald, "Observing New Geometric Phases in the Lab", Physics Today, Vol. 71, #10, Oct. 2018, p. 21.

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