Question

Two electrons are moving towards each other, each with
moving towards each other, each with a velocity of 10 ms. What will be
closest distance of approach between them?

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Answer 1

At the closest distance of approach the kinetic energy of both the electron will be converted into the electrostatic potential between the two electron at that moment.

=2.(1/2 .mass of an electron . (106)2) = 1/(4.π.ε) (charge of electron)2 /(r)

Solve the above equation for r. here ε is permittivity constant.

Hope may help you