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after an initially neutral glass rod is rubbed with an initially neutral silk scarf, the rod has a charge of 89.0 µc. estimate the fractional increase or decrease in the scarf's mass. (assume the scarf had a mass of 100 g.)
delta m / m = ?
would this change in mass be easily noticed? (assume that this change is noticeable if it is more than 1 mg.)
yes or no

5.062 x 10^-9 mg

Explanation:

Charge on glass rod = 89 uC

Charge on silk cloth = - 89 uC

mass of scarf, M = 100 g

Number of excess electrons on silk cloth = charge / charge of one electron

n = (89 x 10^-6) / ( 1.6 x 10^-19)

n = 5.5625 x 10^14

mass of one electron = 9.1 x 10^-31 kg

Mass of  5.5625 x 10^14 electrons =  5.5625 x 10^14 x 9.1 x 10^-31 kg

ΔM = 5.062 x 10^-16 kg

Δ M / M = (5.062 x 10^-16) / 0.1 = 5.062 x 10^-15 kg = 5.062 x 10^-9 mg

It is not noticeable.