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V
ValeryOchkov24-Ruby IV
24-Ruby IV
November 4, 2021
Question

Boundary problem with f(x):=Odesolve...

  • November 4, 2021
  • 2 replies
  • 2619 views

I would like to solve one ODEs boundary problem (find v) with using user functions based on the Odesolve function.

But

1. Cannot use root or Find functions

2. Very slowly calculation

3. I must restart my Prime 6

etc

Help please!

PS

I cannot write this problem in Polar coordinates! See attach.

2 replies

F
Fred_Kohlhepp23-Emerald I
23-Emerald I
November 4, 2021

One error:

Fred_Kohlhepp_0-1636030041033.png

By inspection r(0 s) = a

L
LucMeekes23-Emerald IV
23-Emerald IV
November 4, 2021

No,

at t=0, the comet is at (-a,0), its distance to the sun (r) then is a+c.

 

Luc

F
Fred_Kohlhepp23-Emerald I
23-Emerald I
November 5, 2021

You're right, as usual!

I need to read more carefully.

L
LucMeekes23-Emerald IV
23-Emerald IV
November 4, 2021

How about (Mathcad 11, cannot use units):

LucMeekes_0-1636062694602.png

LucMeekes_2-1636062773936.png

LucMeekes_3-1636062843451.png

Calculate the speed from the x and y speeds:

LucMeekes_5-1636062927300.png

Success!
Luc

 

 

 

    V
    ValeryOchkov24-Ruby IVAuthor
    24-Ruby IV
    November 5, 2021

    Thanks, Luc!

    No problem with X-Y-coordinats

    Problems with Polar - see please pdf in attach (and Prime 6)

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