Here's a question from my textbook:(adsbygoogle = window.adsbygoogle || []).push({});

Two copper spheres, each having a mass of .4 kg, are separated by 2 m.

(a) How many electrons does each sphere contain? The atomic mass of copper is 63.5 g/mol, and its atomic number is 29.

(b) How many electrons would have to be removed from one sphere and added to the other to cause an attractive force of 1.00x10^4 N (roughly 1 ton)?

I got (a) by dimensional analysis:

(.4 kg Cu) x (1 mol/.0635 kg Cu) x (6.02x10&23 molec/1 mol) x (29 electrons/molec) = 1.10x10^26 electrons

But, I am having trouble with part (b). I was thinking that you should use the equation:

F=k(q_1)(q_2)/r^2 , but I'm not really sure how to proceed. I would appreciate any help. Thanks so much!

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# Homework Help: Coulomb's Law of two copper spheres

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