The Problems With Relativistic Mass

relativistic mass is how hard you are to push at all speeds. It's just a number whereas momentum is three numbers it's a direction and so if you have a high speed in one direction you basically have a different relativistic Mass in each direction because it's harder to push you in the direction you're already going fast then it is to push you perpendicular to the head direction. So then you need like a transverse relativisticmass and a longitudinal relativisticMass which gets messy very quickly.