Table of Mechanics Demonstration

List of Mechanics Equipment & Supplies

Lecture Demonstrations

Rotating Platform and Dumbbells, 1Q40.10

Topic and Concept:

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An instructor or volunteer stands on a rotating platform holding a set of dumbbells. While rotating, he or she extends and retracts his or her arms while rotating causing the angular speed to change.



ID Number

Rotating Platform

ME, Bay B9, Shelf #1


ME, Bay B9, Shelf #2

Important Setup Notes:

Setup and Procedure:

  1. Set Rotating Platform out on the floor.
  2. Level the platform using the bubble level in the center of it(see photo) by adjusting the relative heights of the three brass feet.
  3. Have the volunteer carefully step on to the rotating platform.
  4. Hand the volunteer the pair of dumbbells, and have him or her hold one in each hand straight out from his or her sides to make a "T shape".
  5. Make sure it's okay with the volunteer to give him or her a little spin. If it is, then give the volunteer a little push to set him or her spinning. Otherwise, you'll need a new volunteer.
  6. Once spinning, have the volunteer slowly bring his or her arms in close to the center of rotation. The rotational speed will increase.
  7. Have the volunteer extend his or her arms again, and observe that the rotational speed assumes (close to thanks to friction) its original value.
  8. To stop the volunteer, let him or her know that you are going to stop his or her spinning. Do so by gently grabbing his or her shoulders. If this is set up next to the lecture bench, the volunteer can stop alone by grabbing the lecture bench in passing.

Cautions, Warnings, or Safety Concerns:










fw: Rotating_Platform (last edited 2018-07-18 17:22:11 by srnarf)