Inertia of Rest  - Mass and String


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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.

Condition :   Good  
Principle :   Inertia of Mass   
Area of Study :  Mechanics  
Equipment :   6" string lengths, 1 K mass, 12" iron handle, foam pads.

Procedure :   Hang the mass from one of the strings.  Attach another string from the bottom of the mass and to the other end of this string attach the handle.  Pulling slowly on the handle will break the top string.  Jerking on the handle will break the bottom string.

An easier way to demonstrate this would be to use a single string.  Attach the string to the mass and slowly pull upward lifting the mass off the table.  Repeating this process trying to jerk the mass upward will break the string.  

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Mark A. Heald and George M. Caplan,  "Which String Breaks?",  TPT, Vol. 34, # 8, p. 504, November 1996.

Martin Gardner, "Which Thread?", TPT, Vol. 33, # 7, Oct. 1995, p. 478.

Gerald Hodgon, "Golden Oldie" Newton's First Law Demonstration", TPT, Vol. 32, # 2, Feb. 1994, p. 117.

Peter W. Sullivan, "Inertia Demo With a Flair Pen", TPT, Vol. 31, # 7, Oct. 1993, p. 427.

Martin Gardner, "Frustrating Papers", TPT, Vol. 29, # 6, June 1991, p. 416.

Allan Franklin, "Inertia in the Middle Ages", TPT, Vol. 16, # 3, Mar. 1978, p. 201.


George M. Caplan, "Ye Olde Inertia Demonstration", AJP, Vol. 72, # 7, July 2004, p. 860.

Frank G. Karioris, Inertia Demonstration Revisited", AJP, Vol. 46, # 7, July 1978, p. 710.

P. LeCorbeiller,  "Notes and Discussion: A Classical Experiment Illustrating the Notion of 'Jerk'",  AJP, 14, p. 64, 1946.

P. LeCorbeiller,  "A Classical Experiment Illustrating the Notion of 'Jerk'",  AJP, 13, p. 156, 1945. 


Mc- 2,  Freier and Anderson,  A Demonstration Handbook for Physics. 


M- 250,  "Break String with Large Mass",  DICK and RAE Physics Demo Notebook.


Charles Vivian, "More Inertia", Science Experiments & Amusements For Children, p. 91.

Martin Gardner, "Which Thread?", Science Tricks, p. 43.

Julien Clinton Sprott, Physics Demonstrations,  "1.5, Inertia Ball",  p. 13, ISBN 0-299-21580-6.

Robert Ehrlich,  "Pulling a Thread Attached to a Hanging Weight",  Turning the World Inside Out, p. 30.

Mail Questions and Comments to:  Dale Stille