1Q60.40 - Stable and Unstable Axis of Rotation - Toss the Block

Code Number:
Demo Title:
Stable and Unstable Axis of Rotation - Toss the Block
Center of Mass
Area of Study:
Rectangular Styrofoam or wooden block or book.

You can use either the large Styrofoam block or a smaller wooden block for this demonstration.

The block has 3 axis of rotation.  Stable rotation can be found around two of the axis and unstable rotation will be found in the third axis.  This instability will be shown by a wobble when spun about that axis.

  • Matthew Loth, Chad Gibbons, Sami Belaiter, and James B. Clarage, "Stable and Unstable Rotational Dynamics of a Smartphone", TPT, Vol. 55, #7, Oct. 2017, p. 431.
  • D.A. Wardle, "Unstable Rotation of Rigid Bodies in Empty Space", TPT, Vol. 39, #6, Sept. 2001, p. 334.
  • Mellisa Arndt, Thomas Mortenson, and Jearl Walker, "Why Does a Spinning Book Wobble?", TPT, Vol. 19, #1, Jan. 1981, p. 57.
  • John B. Hart, "Great Ellipsoids of Inertia and Space Physics", TPT Vol. 6, #3, Mar. 1968, p. 118.
  • Michael S. Wheatland, Tara Murphy, Daniel Naoumenko, Daan va Schijndel, Georgio Katsifis, "The Mobile Phone as a Free-Rotation Laboratory", AJP, Vol. 89, #4, April 2021, p. 342.
  • Robert H. Romer, "Demonstration of the Intermediate-Axis Theorem", AJP, Vol. 46, #5, May 1978, p. 575.
  • R. W. Pohl, Physical Principles of Mechanics and Acoustics, p. 114.
  • Jearl Walker, "1.96, Spinning a Book", The Flying Circus of Physics Ed. 2, p. 48.
  • Jearl Walker, "Spinning a Book", The Flying Circus of Physics with Answers.

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