MathGroup Archive 2014

[Date Index] [Thread Index] [Author Index]

Search the Archive

Three masses and four springs


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]



  • Prev by Date: Speed of Join and Append. Was Re: Simple list question
  • Next by Date: Re: Three masses and four springs
  • Previous by thread: Speed of Join and Append. Was Re: Simple list question
  • Next by thread: Re: Three masses and four springs