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Three masses and four springs

• To: mathgroup at smc.vnet.net
• Subject: [mg132597] Three masses and four springs
• From: Robert Jenkins <dale.jenkins8 at gmail.com>
• Date: Wed, 16 Apr 2014 03:40:27 -0400 (EDT)
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The instruction
DSolve[{-2*x1[t] + x2[t] == x1''[t], -2*x2[t] + x1[t] == x2''[t], 
  x1[0] == -1, x2[0] == 2, x1'[0] == 0, x2'[0] == 0}, {x1, x2}, t]
produces a simple solution. But I am surprised to find the three-mass version produces a mass of complication. Have I made a mistake?
DSolve[{-2*x1[t] + x2[t] == x1''[t], -2*x2[t] + x3[t] + x1[t] == 
   x2''[t], -2*x3[t] + x2[t] == x3''[t], x1[0] == -1, x2[0] == 2, 
  x3[0] == -1, x1'[0] == 0, x2'[0] == 0, x3'[0] == 0}, {x1, x2, x3},
  t]

• Follow-Ups:
  • Re: Three masses and four springs
    • From: Bob Hanlon <hanlonr357@gmail.com>