Mass and Speed in Special Relativity

elec-tric
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is the mass invariant in special relativity or what ?
i'm so confused , is the mass of a body change with the change of the body's speed ?
 
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Two different conventions are being used. The one favored by most people today is this one:

Mass is invariant. It's denoted by m. The quantity

\frac{mc^2}{\sqrt{1-\frac{v^2}{c^2}}}

is called "energy". If we have to use a name for the quantity

\frac{m}{\sqrt{1-\frac{v^2}{c^2}}}

we call it "relativistic mass", but we prefer not to use it at all.

The other convention is to use the notation m_0 and the term "rest mass" for what I would call "mass", and the notation m for what I would call "relativistic mass". This convention makes "mass" a function of speed:

m=\frac{m_0}{\sqrt{1-\frac{v^2}{c^2}}}
 
elec-tric said:
is the mass invariant in special relativity or what ?
i'm so confused , is the mass of a body change with the change of the body's speed ?

Please read an entry in our FAQ in the General Physics forum.

Zz.
 

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