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GR0177 #92
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Alternate Solutions |
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Comments |
jmason86
2009-07-05 20:04:03 | If you didn't know the potential energy of the spring, you could derive it from Hooke's law.
In general,  , so
What I don't get is that the negative in Hooke's law doesn't just disappear because you integrate.. so why is potential energy stored in a spring defined to be positive? This would lead to the incorrect answer of (D).
jmg810
2009-07-08 14:19:25 |
If a force is derivable from a position dependent potential then  = - ( ), and hence  .
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jmg810
2009-07-09 09:20:29 |
Typo fix:
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jmason86
2009-07-23 17:36:11 |
Thanks!
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|  | neutrino
2007-10-31 03:34:57 | I don't understand the signs. If the string is ``fully stretched",  , but  is max. I would guess answer D in this case.
What is my error?
hot_dark_matter
2008-05-23 15:00:49 |
If the spring is fully stretched, it doesn't mean that the kinetic energy is zero. Presumably, the directions of  and  indicate the system can have translational and rotational energy.
As for the signs, kinetic energy is always positive and so is the potential energy stored by a spring. This eliminates all choices but (B) and (E). Given that there is only one spring, the answer must be (E).
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