GR9277 #44



Alternate Solutions 
rrfan 20111106 12:45:34  The Lagrangian is , where and . Only choices (A) and (B) contain . Of these two, only (A) is possible because must be greater than or equal to .  

Comments 
rrfan 20111106 12:45:34  The Lagrangian is , where and . Only choices (A) and (B) contain . Of these two, only (A) is possible because must be greater than or equal to .
RusFortunat 20151022 16:32:57 

  Quark 20111026 15:17:39  This is probably a silly question but, why would one be wrong in choosing choice (E)? I actually picked the right answer (A) on the test but glancing over it again, (E) is also correct in the most general form. Is it not explicit enough? lol
rrfan 20111106 13:14:00 
the +mgy is wrong.

livieratos 20111108 14:41:41 
also if i remember correctly, since the two coordinates of each other the Lagrangian has to be dependent only on one of them and on its time derivative, not both...
but i could be wrong. guess i should read lagrange and hamilton again :P

  $null 20091028 16:39:52  Reposted to section...(with sexy LaTeX)
There is a typo in Answer A, it should be , not   tan 20091014 23:52:17  There is a typo in Answer A, it should be y dot, not y double dot.   mdornfe1 20081106 16:58:28  This can be done by noticing that potential energy has to be mgy. A and B are only answers with this property. Second the kinetic energy must always be positive 1(4ay)^1 is not always positive. So choice A is the answer.
his dudeness 20100904 13:42:09 
well done, brah

TeamGandalf 20110401 18:12:40 
The Lagrangian is equal to TV. Why doesn't the negative from the Potential cancel the negative in the equation?
Why isn't it L = T  (mgy)= T + mgy?

Quark 20111026 15:20:37 
@TeamGandalf
The lagrangian is L = T  U. You can't have a negative potential energy... U=mgy not (mgy).

  Poop Loops 20081012 00:45:40  So what happens when y = 0, as it inevitably will when the particle comes back down?
segfault 20090904 12:14:26 
(I realize I'm replying to a 1 year old postthis is for the general public). When y>0, the term will blow up but will be zero, so L won't blow up. Perhaps if L was written in terms of it would have a nicer form...

  etano 20070616 14:12:37  There is a typo in Answer A, it should be y dot, not y double dot.  

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