Timeline for Is it possible to conserve the total kinetic energy of a system, but not its momentum?
Current License: CC BY-SA 4.0
9 events
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| Dec 19, 2019 at 14:47 | history | edited | BioPhysicist | CC BY-SA 4.0 |
added 18 characters in body
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| Dec 19, 2019 at 2:19 | comment | added | user76284 | @DaveInCaz I don’t think your spinning ball (as a whole) is undergoing uniform circular motion. A chunk of that ball may be undergoing uniform circular motion, but it is obviously not isolated, as it is attached to the rest of the ball. | |
| Dec 18, 2019 at 21:01 | comment | added | BioPhysicist | @DaveInCaz At that point the system is all of the particles that make up that body. The total momentum would then be constant as no net force is acting on the spinning body. | |
| Dec 18, 2019 at 13:17 | comment | added | BioPhysicist | @Peteris I never said anything about a single isolated object. Furthermore, what you define as "the system" is subjective. I have defined my example system as an object experiencing an external force causing the object to undergo uniform circular motion. You can always widen your scope to include enough to say everything is conserved, but that doesn't mean everything is conserved for all systems. | |
| Dec 18, 2019 at 12:13 | comment | added | StayOnTarget | @Peteris couldn't a single rotationally symmetric object spinning about its center of mass be undergoing uniform circular motion? | |
| Dec 18, 2019 at 11:59 | comment | added | Peteris | Well, but an isolated object can't be undergoing uniform circular motion - it can do only because it's attracted by something else, but it's equally attracking that something, changing its momentum. If it's in circular motion because it's orbiting something, then the momentum of the total system (e.g. earth-moon) would be conserved. So it's pretty much a tautology "momentum of a system can be changing if it's caused by an interaction with another system changing its momentum in exact opposite way". | |
| Dec 17, 2019 at 19:34 | vote | accept | Petru Neagu | ||
| Dec 17, 2019 at 19:31 | comment | added | dmckee --- ex-moderator kitten | I was coming to discuss the Earth-moon system (or any orbitting cluster) as an example of this cases. | |
| Dec 17, 2019 at 19:25 | history | answered | BioPhysicist | CC BY-SA 4.0 |