Question

If in the process oof rubbing the lenses of the eyeglasses, 6.28 x 10^10 electrons were transferred,

a) what is the charge of the lenses and the nylon cloth?

b) what is the change in their masses?

Answer 1

The charge of the lenses (glass) is positive

$$q_1=eN\\ =1.6\times 10^{-19}\:\rm C\times 6.28\times 10^{10}=1.00\times 10^{-8}\:\rm C$$

The charge of the nylon cloth is negative

$$q_2=-eN\\ =-1.6\times 10^{-19}\:\rm C\times 6.28\times 10^{10}=-1.00\times 10^{-8}\:\rm C$$

The change in mass

$$\Delta m=Nm_e\\ =6.28*10^{10}*9.1*10^{-31}\:\rm kg=5.71*10^{-20}\: kg$$

The lenses lose, the nylon cloth gains.