how many electrons should be removed from each of the two similar spheres each of 10 gram so that electrostatic repulsion is balanced by the gravitational force?
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We know that gravitational force is equal to Gm1m2/r2 and also electrostatic force is equal to Kq1q2/r2.
Since both are equal so,
Gm1m2/r2 = Kq1q2/r2
Multiplying r2 both sides,
Gm1m2 = Kq1q2
since m1=m2=0.01Kg, G=6.67x10-11, K=9x109 and q1=q2 so,
(6.67x10-11)(0.01)2 = (9x109)q2
6.67x10-15 = (9x109)q2
q2 = (6.67x10-15)/(9x109)
q2 = 0.741x10-24
q = 0.86x10-12
q is charge and we have to find number of electrons (n), this can be done by the formula:
q = ne, where n is a number of electrons and e is charge of electron.
n = q/e
n = (0.86x10-12)/(1.6x10-19)
n = 0.537x107
n = 5.37x106 (Ans)
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