Rolling Chain, 1D50.70

Topic and Concept:

• Motion in Two Dimensions, 1D50. Central Forces

Location:

• Floor Item: ME, South Wall

  

Abstract:

A flexible chain is spun on a motorized Disk. When pushed off the disk, it maintains it's rigidity as it rolls across the lecture bench. A block is put in its path to make it jump.

Important Setup Notes:

• This demonstration requires practice.

Setup and Procedure:

1. Position the cart so that the spiral pattern on the turning wheel will face the audience.
2. The ramp, which is hanging off the side of the cart, has two holes on one end which will sit on corresponding pins located under the rotating wheel. The opposite end will sit on the lecture bench - make sure the ramp is lined up parallel with the table.
3. Plug in the motor.
4. Place the chain on the soon-to-rotate wheel.
5. Turn on the motor, and let it reach a stable speed.
6. Using the plastic ruler, gently nudge the chain off the wheel. The chain will then roll down the ramp and onto the table.
7. Turn off the motor.

Cautions, Warnings, or Safety Concerns:

• Do NOT launch the chain into the audience!

Discussion:

When the chain is rotated about center on the wheel at high enough speed, each individual chain link splays outward due to the centrifugal "force". There is a force on each chain link from its two neighboring links which keeps the link from flying off tangentially from the rotating wheel. The net effect of this is a virtually rigid loop. This rigidity is made apparent as the chain rolls down the ramp, hits a block, and becomes temporarily airborne. Upon landing, the loop again assumes its course rolling along the bench.

Videos:

• Lecture Demonstration's Youtube Channel

References:

• Central Forces - Wikipedia

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