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need help determined time to travel a path

• To: mathgroup at smc.vnet.net
• Subject: [mg107512] need help determined time to travel a path
• From: "bwalker at musings.com" <brad2000 at gmail.com>
• Date: Mon, 15 Feb 2010 05:47:53 -0500 (EST)

I am trying to determine the time to travel a circular path. This path is on a
circle. It's fairly easy to understand.

But, I can't seem to figure out why this is failing.

(* define my parametrizations *)
circlex[t_]:=13+13*Sin[t+pi];
circley[t_]:=13+13*Cos[t+pi];

(* the derivatives *)
dcirx[t_]:=D[circlex[t],t];
dciry[t_]:=D[circley[t],t];


(* amount of time needed to travel a circle *)
Integrate[Sqrt[(dcirx[t])^2+(dciry[t])^2]/Sqrt[2*g*(circley[time0]-
circley[t])], {t, 0.01, pi/2}]

I get a negative value for the time. This can't be right..

Any help is much appreciated!!

Thanks.

Brad Walker

• Follow-Ups:
  • Re: need help determined time to travel a path
    • From: Murray Eisenberg <murray@math.umass.edu>
  • Re: need help determined time to travel a path
    • From: Brad Walker <bwalker@musings.com>
  • Re: need help determined time to travel a path
    • From: Tomas Garza <tgarza10@msn.com>