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Timeline for Paradox in simple homework problem

Current License: CC BY-SA 3.0

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Jun 13, 2017 at 12:29 vote accept PhyEnthusiast
May 26, 2017 at 5:08 comment added John Rennie @PhyEnthusiast: that's the sort of thing we should take to the chat room
May 26, 2017 at 5:07 comment added PhyEnthusiast ok, got the answer. But, I have another question now. How to calculate that the maximum extension will be $\frac{2mg}{k}$?
May 26, 2017 at 4:58 history edited John Rennie CC BY-SA 3.0
Extend answer
May 26, 2017 at 4:46 comment added John Rennie @PhyEnthusiast: if you do that the mass/spring system oscillates around an average extension of $\Delta mg/k$. When the mass has reached a displacement of $\Delta x$ it has kinetic energy as well as potential energy. The kinetic energy is $mg\Delta x$ minus the work done by the spring $\tfrac{1}{2}k\Delta x^2$.
May 26, 2017 at 4:45 history edited John Rennie CC BY-SA 3.0
Extend answer
May 26, 2017 at 4:42 comment added PhyEnthusiast ok, but what if I hook the block onto the spring and leave the system to reach equilibrium, I do no work on the system. And then what I did is justified [I hope].
May 26, 2017 at 4:36 history answered John Rennie CC BY-SA 3.0