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MathGroup Archive 2002

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inverse square law attraction

  • To: mathgroup at smc.vnet.net
  • Subject: [mg34884] inverse square law attraction
  • From: "Dick Boardman" <boardman at onetel.net.uk>
  • Date: Tue, 11 Jun 2002 05:01:02 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

I have a question I would be pleased if someone would answer.

I am studying planetary motion under the inverse square law attraction.

I use NDSolve to find the numerical solution to

y''[t]====-y[t]/(x[t]^2+y[t]^2)^(3/2)
x''[t]====-x[t]/(x[t]^2+y[t]^2)^93/2)
x'[0]==0
y'[0]==1.2
y[0]==0
x[0]==1

And get a very satisfactory ellipse. However, I would like to check the hodograph
( a parametric plot of x'[t] and y'[t]
against time. NDSolve must have calculated values for x'[t] and y'[t] but I
 cannot find them. Where are they please?

R.M.Boardman


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