Timeline for Why does gravity act at the center of mass?
Current License: CC BY-SA 3.0
19 events
| when toggle format | what | by | license | comment | |
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| Apr 27, 2017 at 13:39 | comment | added | Meep | As stated above, gravity acts on all points of an object. But since the force experienced is proportional to the mass of some element in a body (or a particle of a multi-particle system), and in calculating the centre of mass the contribution from the element is also protportional to its mass, the total force experienced by a multi-particle system is equivalent to one acting at the 'COM' on a mass equal to the total mass of the system. If the force were proportional to mass squared, this wouldn't be the case. | |
| Apr 27, 2017 at 7:14 | comment | added | TripeHound | And the reason "using the COM" doesn't work on the seas is (as noted in @anaximander's comment to ubuntu_noob's answer) is that they aren't a rigid body. Modelling gravity through the COM only works when the object itself won't deform. | |
| Apr 27, 2017 at 3:09 | history | tweeted | twitter.com/StackPhysics/status/857431355520671744 | ||
| Apr 26, 2017 at 19:53 | answer | added | Steeven | timeline score: 2 | |
| Apr 26, 2017 at 19:23 | history | protected | Qmechanic♦ | ||
| Apr 26, 2017 at 18:59 | answer | added | Sarit Sotangkur | timeline score: 0 | |
| Apr 26, 2017 at 13:46 | comment | added | Jyrki Lahtonen | It doesn't. That's one of the reasons why we have tides. The Moon pulls water closer to it a bit more strongly than it does the center of Earth and the water on the opposite side a bit more weakly. That's why sea levels rise a bit on both sides in comparison to what it is in-between. | |
| Apr 26, 2017 at 12:57 | comment | added | James | It doesn't. As you've stated gravity acts on all points. However, the problem can be modeled as an equivalent system where the net force acts upon the COM of the object. ubuntu_noob shows the mathematical proof. The key here is modeling--a simplified problem that represents the behavior of reality. | |
| Apr 26, 2017 at 12:23 | answer | added | Charles Jacks | timeline score: 2 | |
| Apr 26, 2017 at 3:47 | vote | accept | Ahmed S. Attaalla | ||
| Apr 26, 2017 at 3:43 | comment | added | dmckee --- ex-moderator kitten | Closely related: physics.stackexchange.com/q/151402 | |
| Apr 26, 2017 at 3:22 | history | edited | Qmechanic♦ | CC BY-SA 3.0 |
deleted 17 characters in body; edited tags
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| Apr 26, 2017 at 2:35 | answer | added | Farcher | timeline score: 13 | |
| Apr 26, 2017 at 2:26 | answer | added | Luke Pritchett | timeline score: 10 | |
| S Apr 26, 2017 at 1:31 | history | suggested | Ghosal_C | CC BY-SA 3.0 |
fixed grammar
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| Apr 26, 2017 at 1:11 | answer | added | Ghosal_C | timeline score: 31 | |
| Apr 26, 2017 at 0:54 | review | Suggested edits | |||
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| Apr 26, 2017 at 0:54 | answer | added | JEB | timeline score: 14 | |
| Apr 26, 2017 at 0:29 | history | asked | Ahmed S. Attaalla | CC BY-SA 3.0 |