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reyrey389
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http://faculty.mint.ua.edu/~pleclair/ph125/Misc/exam2_form_a_solns.pdf
On page 1, problem 1, where it shows a mass M and another mass 3M connected by a cord and spring. Then the cord is burned off, and then the spring "pushes the blocks away" I get the momentum conservation and how to work the problem, but I don't get why the springs would behave like this and push the blocks? If the blocks were at rest initially, then the spring is neither stretched nor compressed, it is at its relaxed state and so it has no energy at all. But even if it did, this would come from kinetic energy of the blocks moving to the left/right, and stretching the spring to the left/right, so then the moment the cord is cut , wouldn't the spring *pull* the blocks towards each other ?
Thanks
On page 1, problem 1, where it shows a mass M and another mass 3M connected by a cord and spring. Then the cord is burned off, and then the spring "pushes the blocks away" I get the momentum conservation and how to work the problem, but I don't get why the springs would behave like this and push the blocks? If the blocks were at rest initially, then the spring is neither stretched nor compressed, it is at its relaxed state and so it has no energy at all. But even if it did, this would come from kinetic energy of the blocks moving to the left/right, and stretching the spring to the left/right, so then the moment the cord is cut , wouldn't the spring *pull* the blocks towards each other ?
Thanks