Which Is Harder Work?
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From: Yorba Linda, CA
Originally Posted by Sabre,Dec 26 2007, 07:42 PM
If you start with the longest leg first, by the time you are worn out and exhausted there is only 1 more left. Easier to give that last push "only one more to go".
Now imagine running 1-2-3 and when you get to the bottom of the hill on the 3, turning around and having to go back up all the way to the top "all that way".
Now imagine running 1-2-3 and when you get to the bottom of the hill on the 3, turning around and having to go back up all the way to the top "all that way".
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Originally Posted by magician,Dec 26 2007, 08:23 PM
Even a high school physics student would know that this statement is absurd.
Work is defined as force times distance. (Obviously, when the force is variable this simple formula must be replaced with a definite integral; the following argument is, if anything, even stronger in that case.) The force applied is not zero and the distance covered is not zero. (Please don't try to use a vector argument to claim that the net distance is zero; even in that case the statement is incorrect because the force vector changes direction as well.)
Work is defined as force times distance. (Obviously, when the force is variable this simple formula must be replaced with a definite integral; the following argument is, if anything, even stronger in that case.) The force applied is not zero and the distance covered is not zero. (Please don't try to use a vector argument to claim that the net distance is zero; even in that case the statement is incorrect because the force vector changes direction as well.)
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^^
You're not thinking of work as a unit of measure. Even if you were pushing something the entire distance and ended up back at the starting point, you've used force and covered distance.
You cant just say "since I'm back where I started, I accomplished nothing"
You're not thinking of work as a unit of measure. Even if you were pushing something the entire distance and ended up back at the starting point, you've used force and covered distance.
You cant just say "since I'm back where I started, I accomplished nothing"
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From: Yorba Linda, CA
Originally Posted by Malloric,Dec 26 2007, 09:39 PM
Actually, he's right. Just because you did no work doesn't mean you expended no energy. It's the classic doing work around a square problem. Sum of the F*D vectors does indeed sum to zero. Force is a vector, distance is not. You'll have expended a lot of energy (potential), but achieved no work. I mean think about it... you ended up in the exact same place you started, what work could you have possibly have done?
Work is a scalar quantity, not a vector quantity. Distance - in the form of displacement - is a vector quantity. Work is the scalar (dot) product of the force vector and the displacement vector. In the classic doing work around a square problem if your force vector along each edge of the square points in the same direction as your displacement vector along that edge you've done positive work along each edge; therefore, you've achieved a lot of work: moving an object around a square.
I did think about it. I've also taught it in several multi-variable calculus classes.
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From: Yorba Linda, CA
Originally Posted by Sabre,Dec 26 2007, 10:10 PM
You cant just say "since I'm back where I started, I accomplished nothing"
Personally, I know quite a few people who do tons of work and accomplish nothing.
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Magician first stated that an enthusiastic person who enjoyed running would rather do 1-2-3, however it can always be negative if a person were pessimistic. Often times I like to do the hard parts first so to have the easier, more relaxed parts to finish off with and cool down. If I were to do 1-2-3, after the first I would probably say "Great, now 2 and 3 more of these uphill and downhill", yet if I were to do 3-2-1 after the first 3 I would say "Woot, just three more to go".
Also, since y'all are getting more psychological. You made me think of the greek philosopher Zeno and the paradoxes he brought up. I mean, if You're going to say that if you finish from where you started, then you did no work at all; You're practically saying Life has no meaning and that you don't exist. Do you exist?
Also, since y'all are getting more psychological. You made me think of the greek philosopher Zeno and the paradoxes he brought up. I mean, if You're going to say that if you finish from where you started, then you did no work at all; You're practically saying Life has no meaning and that you don't exist. Do you exist?
