Distance of Electrons with Electrostatic Force

[kgal]

Homework Statement

How far apart must two electrons be placed on the Earth's surface for there to be an electrostatic force between them equal to the weight of one of the electrons?

Homework Equations

Fe = (1 / 4∏ε0) X (q1q2 / r^2)

The Attempt at a Solution

I set Fe = me- (electrical force = mass of electron).

and solved for r = sqrt( q^2 / (me-)(4∏ε0) ) = 15.98 m, but the answer should be 5.08 m..

 

[tiny-tim]

hi kgal!

I set Fe = me- (electrical force = mass of electron).

and solved for r = sqrt( q^2 / (me-)(4∏ε0) ) = 15.98 m, but the answer should be 5.08 m..

hmm … 15.98/5.08 = π …

did you lose a π somewhere?​

 

[technician]

The WEIGHT of an electron = me x 9.81, I got the answer to be 5.02m

 

[kgal]

i attached the picture.

I don't see the flaw...

 

[kgal]

thanks technician!

i thought that i have to ignore g because its so small compared to the electrical forces...