Let us assume one electron as stationary, while the other electron moved towards the first at 2 x 10⁶ m/s (twice the speed of the single electron).

let r represent the minimum distance between the particles. The work required to bring an electron from a distance of infinity to distance r

is =

(Charge on one electron is 1.6 x 10^-19 C)
The electron's original kinetic energy is converted into electrical potential energy.

At the minimum distance apart, the kinetic energy is zero, so all the kinetic energy has been converted into electrical potential energy.

(value of k is 9 x 10⁹)

on solving above equation

we get m