Balancer
   The balancer is an example of a favorite type of physics demonstration: the counter-intuitive situation which makes the student reexamine the fundamental understanding of the phenomena.

   Like most center-of-mass demonstrations, the key to understanding stable equilibrium is that the center of mass of the system must lie directly below the point of support.

   The nicely-finished horse and rider demonstration at the left was sent to me a number of years ago by a Japanese reader of The Physics Teacher, who had read my note (reference below) on balancers. It appears to be a direct copy of a western demonstration from the latter years of the nineteenth century.
 
                 Greenslade Collection                                     Davidson College                                      Smithsonian Institution




   This more rudimentary blancer is in the collection of historical physics teaching apparatus at Case Western Reserve University in Cleveland, Ohio


REF: Thomas B. Greenslade, Jr., "Balancers", The Physics Teacher, 19, 554-555 (1981)

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