On the equations of motion of the folded inextensible string

  • W. Steiner
  • H. Troger
Original Papers


In a number of excellent, even recently published, books in Theoretical Mechanics the equations of motion of a folded inextensible string, for example to explain the crack of a whip, are derived using either the energy principle, if a system of one degree of freedom is considered, or Lagrange's equations for conservative systems, if a system of more than one degree of freedom is studied. However, it will be shown in this paper that the resulting equations are incorrect because physically a nonconservative system is given. Hence, both methods mentioned above based on energy conservation must not be used. A correct derivation of the equations of motion is given by means of the linear momentum balance.


Mathematical Method Energy Conservation Linear Momentum Momentum Balance Conservative System 
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Copyright information

© Birkhäuser Verlag 1995

Authors and Affiliations

  • W. Steiner
    • 1
  • H. Troger
    • 1
  1. 1.Technical University ViennaViennaAustria

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