Find the speed at which the mass of an electron is double of its rest mass.

Explanation

The mass of an elctron at speed v is `= m_0 = (sqrt 1 -v ^(2) /c ^(2) )`
Where m_0 is its rest mass. If `m = 2 m^(0)`
`2 = 1/ ( sqrt 1 -v ^(2) /c ^(2) ) `
or, ` 1 - v^(2) / v^(2) = 1 / 4 `
or, v = (sqrt 3) / 2 c = 2.598 xx 10^(8) m s^(-1)`