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Re: Can someone tell me why NDsolve isn't working here?

• To: mathgroup at smc.vnet.net
• Subject: [mg44066] Re: Can someone tell me why NDsolve isn't working here?
• From: mizrandir at hotmail.com (Mizrandir)
• Date: Mon, 20 Oct 2003 01:13:35 -0400 (EDT)
• References: <bmqplo$rhb$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

I didn't know that Mathematica couldn't deal with systems of
differential equations which included algebraic equations too (aren't
algebraic equations a particular case of differential equations?).
I've checked wolfram.com and it does say that Mathematica 5 can solve
some DAEs, I think I will download the trial version and try it.

miz.

P.S.: Eckhard Hennig said:
>looks to me like a mechanical system where
>energy conservation is important

Yes, it's a two-body dynamic system and energy conservation is
important. In fact, to get an answer to the problem with generic mass
(M), length (L) and radius (R), I think I'll have to solve it using
energy consevation (but then I won't get the answer for a generic time
(t)).