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Space/Science » in reply to Yes, by conservation of momentum and relative speed.

nick hoffman — 9/9/2007 1:03:35 PM (archived)

If a hypothetical planetary rest mass fell from infinity (or simply somewhere far away) then AS IT FELL, the star would be gradually accellerated towards it by Newton's Third Law.

All the momentum contained in the planet falling DOWN towards the star is exactly equalled and opposed by the momentum of the the star falling UP towards the planet.

When they meet, the momentum is cancelled (but not the energy!).

The whole thread (29 posts)

From GALEX: Speeding-Bullet Star Leaves Enormous Streak Across Sky - Marcia - 8/15/2007 10:41:23 PM
- Speed due to planetary impacts? - Robert Clark - 8/17/2007 7:50:25 PM
  - no: conservation of momentum - relative masses. (n/t) - alcaray - 8/17/2007 11:12:01 PM
    - Yes, by conservation of momentum and relative speed. - Robert Clark - 8/21/2007 6:32:49 PM
      - No - nick hoffman - 9/9/2007 1:03:35 PM
        
        Yes. - Robert Clark - 9/9/2007 3:07:49 PM
        
        Hey, take two magnets... - nick hoffman - 9/10/2007 12:34:56 PM
        
        Bob, I've got a wonderful machine to sell you - nick hoffman - 9/10/2007 12:02:20 AM
        
        re: Bob, I've got a wonderful machine to sell you - Robert Clark - 9/10/2007 8:33:17 PM
        
        Did you ever see one of those wonderous machines with the big wheel... - alcaray - 9/9/2007 7:00:40 PM
      - to the extent that a body is accelerated by falling into a red dwarf... - alcaray - 8/22/2007 12:06:09 AM
        
        re: to the extent that a body is accelerated by falling into a red dwarf... - Robert Clark - 9/8/2007 2:53:07 PM
        
        escape velocity has nothing to do with it, and again you ignore momentum - alcaray - 9/8/2007 5:49:53 PM
        
        Escape velocity equals the velocity of impact, it's BECAUSE of momentum the star must be imparted with additional velocity. - Robert Clark - 9/8/2007 10:04:48 PM
        
        I'm afraid these guys are right, Robert. - Hank - 9/10/2007 7:31:35 PM
        
        re: I'm afraid these guys are right, Robert. - Robert Clark - 9/11/2007 12:28:44 AM
        
        There's still the question of the energy. - Robert Clark - 9/10/2007 8:27:59 PM
        
        re: There's still the question of the energy. - ER - 9/10/2007 9:49:29 PM
        
        This is basic physics. (n/t) - alcaray - 9/9/2007 6:54:59 PM
        
        re: This is basic physics. - Robert Clark - 9/10/2007 8:29:48 PM
        
        It is canceled by the energy of the red giant rushing towards the gas giant. - alcaray - 9/10/2007 9:00:07 PM
- My local affiliates... - alcaray - 8/16/2007 5:11:54 PM
  - lambda nu equals cee - Hank - 8/22/2007 2:05:55 PM
    - re: lambda nu equals cee. Hank, I don't know what that means, but I also gave your argument some thought. :)_ (n/t) - Marcia - 9/8/2007 8:27:29 PM
      - lambda nu = c - Hank - 9/9/2007 12:36:29 AM
  - re: My local affiliates... - Marcia - 8/17/2007 1:06:33 AM
- re: From GALEX: Speeding-Bullet Star Leaves Enormous Streak Across Sky - Andrew - 8/16/2007 3:58:01 AM
- re: From GALEX: Speeding-Bullet Star Leaves Enormous Streak Across Sky. - Of course a 'bow shock' is seen. (n/t) - Marcia - 8/16/2007 2:05:00 AM
  - And way beyond our galaxy, two galaxy clusters collide... - New Age Vapors - 8/17/2007 2:36:12 AM

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