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Polar coordinate derivatives

beefbeef Registered User regular
edited December 2008 in Help / Advice Forum
I'm doing a Lagrangian problem, and I'm having trouble remembering polar coordinate stuff.

Specifically, what would be the derivative of theta dot squared with respect to theta?

And what would be the time derivative of theta dot squared?

Also, both of the above questions with r in place of theta?

I've been looking at Wikipedia and Wolfram and not finding either to be much help.

beef on

Posts

  • FuzzywhaleFuzzywhale Registered User regular
    edited December 2008
    are you near a library? I would go get a copy of "thornton and Marion", which is a nice classical mechanics book. i think chapter 6 gets going with the lagrangian formalism.

    so you need to use your rules for partial derviatives.

    If i have some function f(x) then want to find its partial derivative with respect to y, what usually happens?

    as well, what happens to f(x) when i want some d/dx.

    solutions
    theta dot means theta is a function of time so if you d/dtheta that you are going to anihilate it

    d/dt of thetadot^2 should be 1/2thetadot

    if you swap in r and still want d/dtheta and d/dt, thats gonna be zero, as r is usually r(x).

    Fuzzywhale on
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