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Special Relativity}Conservation of Energy

The rest mass for each mass is 4kg. They collide head-on with identical speeds pointing in opposite directions. This implies that the composite mass is at rest. Thus, recalling that the total energy is given by E=\gamma mc^2 and that the rest mass is given by E=mc^2, one has
 2\gamma mc^2 = Mc^2, where M is the composite mass.

The particle travels at v=3c/5, which yields \gamma = 5/4. Plug this in to get M=10/4 \times 4 = 10kg .

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2009-03-22 16:24:17
The two lumps' energies will be "converted" into mass when they collide and stop because we're given that no energy is radiated. Hence, the final mass must be greater than 8 kg. So, we can immediately eliminate options (A), (B), and (C).

So, if you can't figure it out, you can guess and have a 50% chance of getting it right.
2007-10-03 21:31:57
Relativity gives me a headache. :)
2007-10-16 18:38:25
sorry im looking at the solution and getting confused. are you using the equation \gamma = \1/sqrt{1-v^2/c^2}
2007-10-31 12:44:17
yes, bbaker03, if you plug in v = 3c/5 to the equation you wrote for gamma, you get \gamma = 5/4
2007-11-01 10:24:11
Thanks a lot for your help this site is saving my life on this test. Can't thank you all enough.

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