Sprint 2006 Most desired physics explanation post and replies
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motionmountain 2 Posts |
What are the *most unclear* explanations of the |
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| Hamiltonian - | |
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Smeagol 2 Posts |
We wants to know why people prefer to use a nassty Hamiltonian when a perfectly good Lagrangian will do. |
| Hamiltonian - | |
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Anthony 1 Posts |
Well, this is probably the standard argument but here goes. I think the hamiltonian formulation has a subtle difference from the lagrangian formulation in that the free variables (qi's and pi's) are now indepenently allowed to be varied. in the lagrangian of course you have q and qdot which are not indepent. Also in introductory quantum mechanics it is easier to formulate the shrodinger equation in terms of a hamiltonian operator at first. There will come a time where we actually move back to the lagrangian, i.e. when you begin to study field theories and such. Feynman's lagrangian formulation is very popular in that subject. I dont know if this helped but i hope it did a little bit. |
| Hamiltonian vs. Lagrangian - | ||
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 Dave San Marcos, Texas 441 Posts |
A good discussion of the relative merits of the two formulations is discussed in Thornton and Marion, chapter 7. If you are interested in a more detailed discussion, check out chapters 8, 9 and 10 of Goldstein (the standard graduate text for classical mechanics). Try not to become a man of success, but rather try to become a man of value -- Albert Einstein |
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Matt 1 Posts |
Hamiltonian is good for determining constants of motion in systems. Using Poisson brackets and some other nifty stuff, constants of motion can easily be found. |
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suzi 4 Posts |
I came across something while tutoring some physics students, that torque and energy have the same units (N.m or Joules). I never noticed this before, and I am not sure what it means. Is torque a form of energy? Why do we use the units of N.m for torque instead of calling them joules? |
| Torque and Energy - | |
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Spyridon Koutandos 1 Posts |
My name is Spiros from Greece.I believe that the explanation of quantum mechanics gives an answer to your question.Let me first explain that the explanation of quantum mechanics is kept secret within the MENSA club. I do believe that in nature there exist mostly Pressures and torques , while the concept of force is kept only for gravity.In quantum mechanics this is declared by h bar, bar is units of pressure, and psi the wavefunction is pounds per square inch. I still havent found how torque is included in quantum mechanics.Contact me if you have an idea. |
| torque and energy - | |
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Gary Society of Physics... 293 Posts |
Yeah, I've always thought this was cool...I think of it as nature's way of of being efficient (using the same units to do two different things) or perhaps reminding us of the limitations of traditional dimensional analysis...In some real way I think it's probably best to think of the units and the mathematical nature of the quantity (vector, scalar, tensor, pseudo-vector, etc.) together when using dimensional analysis, so Joules are scalar N*m's and torque is measured in vector Nxm's... Adjunct Professor of Physics, Editor of The Physics Teacher, and GWU SPS Chapter Advisor |
| tides - | |
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Gary Society of Physics... 293 Posts |
most texts do a terrible job about explaining the tides...another huge weakness is in the explanation of how batteries work... Adjunct Professor of Physics, Editor of The Physics Teacher, and GWU SPS Chapter Advisor |
| The adventure of physics - on 1300 free pages - | |
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motionmountain 2 Posts |
I worked the previous comments into the new, |
