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								| ![[parent]](https://images.physicslibrary.org/images/uparrow.png) Viewing Message |  |  |  
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| | | ``Re: elastic string question''  
by rspuzio on 2009-03-25 13:31:10 | 
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 |  | | Use conservation of energy.  Neglecting the mass of the string, the total energy comes from three sources:
 kinetic energy of particle, gravitational potential
 of particle, and elastic energy of string.  By
 symmetry, the particle will move on a vertical line
 passing through the midpoint of A and B.  Both when
 the particle is released from rest and when it comes
 back to rest at the lowest point of its travel, its
 kinetic energy is zero.  Hence, the sum of the
 gravitational and elastic energies must be the same
 at both points.
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