Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thebrain13 on 25/10/2011 06:36:39

Title: how fast would these objects approach each other?
Post by: thebrain13 on 25/10/2011 06:36:39

If there was an object traveling .5c relative to earth and it was being approached by an object traveling .9c from the rear relative to earth how fast would the two objects approach one another from the frame of reference of the object traveling .9c?

Title: how fast would these objects approach each other?
Post by: imatfaal on 25/10/2011 12:06:38

v_close = (v_1 - v_2) / (1- v_1.v_2/c^2)

and the pretty version

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Title: how fast would these objects approach each other?
Post by: thebrain13 on 26/10/2011 03:55:48

thanks

Title: how fast would these objects approach each other?
Post by: damocles on 26/10/2011 08:27:59

Two comments:

(1) In using the formula given, it is important to remember that one of the velocities is negative, so in terms of speeds, we have the sum of the two speeds divided by a number greater than 1.

(2) Is the answer for the closing velocity frame independent? I think it might be, but not at all sure. Because I am fairly sure that the formula given is for the closing velocity in Earth frame of reference.