1G10.47 - Modified Atwoods Machine

Code Number:
1G10.47
Demo Title:
Modified Atwoods Machine

Disclaimer

Procedure:

Video Credit: Daniel Reinart.

This modified Atwood's demonstration starts out with both sides in balance as with a regular Atwood's.  The modifications is that there is 340 grams on one side.  The other side has a 40 gram pulley with a 100 gram mass and a 200 gram mass hanging off each end of the string over it.  Connect the 100 and 200 gram masses together with a string so that they can't move and then balance the whole system.  When you burn the string between the two masses the 100 gram mass accelerates upward and the 200 gram mass accelerates downward.  The unexpected observation is that the 340 gram mass will also accelerate downward when the other two masses start to move, although you will need high speed video to see this clearly.  A video at 200 frames per second works nicely.  A neat demo illustrating accelerated reference frames.  

References:
  • Ricardo Coelho, "Experimental Justification of the Poggendorff Experiment", TPT, Vol. 60, #9, Dec. 2022, p. 762.
  • Tomas Kekule, "Poggendorff's Scales - Demonstration of Newton's Laws in a Less Traditional Way", TPT, Vol. 60, #9, Dec. 2022, p. 759.
  • Frank S. Crawford, "'Diagonalization' of a Compound Atwood Machine", AJP, Vol. 55, #6, June 1987, p. 514.
  • Borislaw Bilash II, “Law of Acceleration - Newton's Second Law“, A Demo A Day – A Year of Physical Science Demonstrations, p. 232.

 


Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.