Nuclear Fusion question

[Achernar]

Okay, we’re defining the mass of a system as its total energy in its zero momentum frame? If so, I’m not sure I see yet why this definition is justified, but now I understand most of your comments so far. But not this one:

*Originally posted by Ring *
However in your example… the sum of their masses equals the total energy of the system in the zero momentum frame.

I don’t see why this is true at all. If the individual particles are moving at a speed v = 0.6 (c = 1), then they each have total energy E = 1.25m[sub]e[/sub], and the total energy of the system is E = 2.5m[sub]e[/sub], not 2m[sub]e[/sub]. What am I doing wrong?

[Ring]

*Originally posted by Achernar *
**Okay, we’re defining the mass of a system as its total energy in its zero momentum frame? If so, I’m not sure I see yet why this definition is justified, but now I understand most of your comments so far. But not this one:I don’t see why this is true at all. If the individual particles are moving at a speed v = 0.6 (c = 1), then they each have total energy E = 1.25m[sub]e[/sub], and the total energy of the system is E = 2.5m[sub]e[/sub], not 2m[sub]e[/sub]. What am I doing wrong? **

Nothing, I misread your post. I thought the particles were stationary.