To find the mass of the electron :
Calculate the KE = o.5mass of electron x(o.9c)2 equate to mc2.
m= 0.5mass of electron x 0.81= 0.405 mass of electron.
The mass of electron = rest mass + 0.405 rest mass = 1.405 rest mass
The mass of electron moving near speed of light is actually about 1.405 times.
