If a matter particle having rest mass of mo is traveling at approximately 86% of the speed of light, what would we measure for the mass m of this matter particle at that particular speed? In all...

If a matter particle having rest mass of mo is traveling at approximately 86% of the speed of light, what would we measure for the mass m of this matter particle at that particular speed?

In all nuclear reactions, does it necessarily follow that the number of neutrons going into a reaction must always be equal to the number of neutrons coming out of a reaction?