Please need help with b) and c) Suppose all the electrons in 21 g of copper atom

Question

Please need help with b) and c)

Suppose all the electrons in 21 g of copper atoms were located at the North Pole of the earth and all the protons at the South Pole. The radius of the Earth is 6370 km. Take the mass number of copper to be 64.

(a) How many electrons are in 21 grams of copper?
569797904200 electrons

(b) What would be the magnitude of the total force of attraction exerted on each group of charges by the other?
__ N
(c) What would be the magnitude and direction of the force exerted by the charges at the Poles on a third charge that is equal to the charge at the South Pole, and located at a point of the surface of the Earth at the equator?

__ N

Explanation / Answer

a.)

Total electrons = (21/64)(6.022 * 1023)(29) = 57.30309375 * 1023 electrons

b.)

Total charge on north pole = -[ 57.312609375 * 1023 ] [1.6 *10-19] = 916849.5 C

F = kq2 / (2r)2 = (9*109)916849.52 / (12740000)2 = 46612.217 Kilo Newton

c.)

F = kq2 / (sqrt(2)r)2 = 2*cos(45)(9*109)916849.52 / 2*(6370000)2 = cos(45)(9*109)916849.52 / (6370000)2

= 131839.258 kilo Newton

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