The equation I'm trying to solve is (r^3) * r ''' - G*m*r' = 0

the independant variable is t.

I'm not far along in DE's yet to know how to go about this.

Last edited by winston on Sep-20-2009 at 21:01

Can you not use a Laplace Transform?

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Is r''' the derivative of the derivative of the derivative of r?

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i could use series solution

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Originally posted by winston i could use series solution

You could indeed. Good idea. Post your work after you finish.

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quote:

Originally posted by Brahman Is r''' the derivative of the derivative of the derivative of r?

It's the "third derivative", so yes... have you taken calculus?

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Originally posted by ziptnf It's the "third derivative", so yes... have you taken calculus?

almost done. post your ideas. if you want. i need more coffee...

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Originally posted by ziptnf You could indeed. Good idea. Post your work after you finish.

oi, i need help with matrices; have you taken multivariable caculus?

Last edited by winston on Sep-20-2009 at 14:12

quote:

Originally posted by winston The equation I'm trying to solve is (r^3) * r ''' - G*m*r' = 0 the independant variable is t. I'm not far along in DE's yet to know how to go about this but I was bored and trying to derive something and came across it.

This to me looks like a nonlinear differential equation. I don't think there's an easy way to solve this.

Are you sure there's a product term involving r^3 * r''' ?

Has this come out of a mechanics problem ? G,m,r are classic variables used to represent gravitational constant, mass and distances.

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Originally posted by ziptnf Can you not use a Laplace Transform?

I don't think so.

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Originally posted by winston oi, i need help with matrices; have you taken multivariable caculus?

Yes, I took Linear Algebra. What do you need help with?

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quote:

Originally posted by Omega_M This to me looks like a nonlinear differential equation. I don't think there's an easy way to solve this. Are you sure there's a product term involving r^3 * r''' ? Has this come out of a mechanics problem ? G,m,r are classic variables used to represent gravitational constant, mass and distances.

Good point, I could use Maple or Matlab to tackle this, because I can't really depend on elementary methods now.

Last edited by winston on Sep-20-2009 at 17:07

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