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# Rotating Gizmo, 3A40.18

Topic and Concept:

• Newton's First Law, [:Newtons1STLaw#InertiaofRest: 1F20. Inertia of Rest]

Location:

attachment:Gizmo09-400.jpg

Abstract:

A device operated with a hand crank causes two small, circular discs to move in simple harmonic motion. One disc moves in a circular path while the other moves in a vertical line showing the physical correspondence of SHM with the "unit" circle (sinusoidal functions).

 Equipment Location ID Number Rotating Gizmo [:MechanicsCabinetBayA11: ME, Bay A11, Shelf T]

Important Setup Notes:

• N/A

Setup and Procedure:

1. Place device on tabletop and operate with the hand crank.

Cautions, Warnings, or Safety Concerns:

• N/A

Discussion:

When the crank is turned, both discs move. One disc moves in a circle while the other moves in a vertical line. The period of oscillation for each disc depends on the speed at which the crank is turned. Regardless of the crank speed, the period of oscillation for each disc will always be the same. This shows how a 1D SHO, or more generally any SHO, can be represented with a sinusoidal function. Such functions have their domain on the unit circle, which is represented by the circularly moving disc.

 attachment:Gizmo01-250.jpg attachment:Gizmo02-250.jpg attachment:Gizmo03-250.jpg attachment:Gizmo04-250.jpg attachment:Gizmo05-250.jpg attachment:Gizmo06-250.jpg attachment:Gizmo07-250.jpg attachment:Gizmo08-250.jpg

Videos:

References:

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