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Math Forum » Discussions » Software » comp.soft-sys.math.mathematica

Topic: NDSolve bug?
Replies: 1   Last Post: Aug 18, 2012 3:44 AM

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DC

Posts: 77
Registered: 8/22/07
Re: NDSolve bug?
Posted: Aug 18, 2012 3:44 AM
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Removing the `=` in the inequalities seems to work :

g = 9.81;
b = 0.;
c = 1.0;

x0 = 0.001;
v0 = 1.001;

sol = First[
x /. NDSolve[{x''[t] ==
Piecewise[{{-g - b*x'[t], x[t] > 0 && x'[t] > 0}, {-g - c*x'[t],
x[t] > 0 && x'[t] < 0}, {g - b*x'[t],
x[t] < 0 && x'[t] < 0}, {g - c*x'[t],
x[t] < 0 && x'[t] > 0}}, 0.], x'[0] == v0, x[0] == x0},
x, {t, 0, 1}, MaxSteps -> \[Infinity], AccuracyGoal -> 3]]

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