Timeline for $F=ma$ contest problem on angular momentum [closed]
Current License: CC BY-SA 3.0
13 events
| when toggle format | what | by | license | comment | |
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| Jan 7, 2015 at 13:27 | history | closed |
John Rennie Neuneck pho ACuriousMind♦ Kyle Kanos |
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| Jan 7, 2015 at 10:54 | answer | added | David Hammen | timeline score: 0 | |
| Jan 7, 2015 at 9:59 | review | Close votes | |||
| Jan 7, 2015 at 13:27 | |||||
| Jan 7, 2015 at 8:39 | history | edited | Qmechanic♦ | CC BY-SA 3.0 |
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| Jan 7, 2015 at 8:07 | answer | added | Numoru | timeline score: 1 | |
| Jan 7, 2015 at 5:41 | comment | added | CuriousOne | You don't need to specify an axis to compare before and after. You can, if you want to. I picked the center of mass system in which both bodies rotate in the same direction before they get in contact and neither rotates after. | |
| Jan 7, 2015 at 5:20 | comment | added | math_lover | I agree with that. But you said "its easy to see that it is not conserved" without specifying an axis. As I said, you can choose an axes such that it is conserved, but that would not be helpful for solving the problem. | |
| Jan 7, 2015 at 5:12 | comment | added | CuriousOne | You can pick the axis of the larger disk as your reference. The process of bringing the smaller disk into contact with the large one will result in a torque on the small disk, so that without an external torque the small disk will end up rotating around the large one. Or maybe I don't understand the setup correctly? | |
| Jan 7, 2015 at 5:09 | answer | added | John Alexiou | timeline score: 3 | |
| Jan 7, 2015 at 5:07 | comment | added | math_lover | Actually angular momentum is with respect to a chosen axes. Suppose you chose the axes passing through the centers of each disk. If you bring the disks together along this axes, angular momentum actually is conserved. | |
| Jan 7, 2015 at 5:04 | comment | added | CuriousOne | Angular momentum conservation has nothing to do with axes, however, it's easy to see that angular momentum is not conserved. Both disks are rotating in the same direction, angular momentum is additive, so it's not the same before the disks contact (it's positive) and after (when it is zero). | |
| Jan 7, 2015 at 4:55 | history | edited | John Alexiou | CC BY-SA 3.0 |
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| Jan 7, 2015 at 4:43 | history | asked | math_lover | CC BY-SA 3.0 |