An attractive force of 7.2 n occurs between two charges that are 0.20 m apart. if one charge is 4.0 μc, what is the other charge?

F = ko *Q_1 * Q_2 / d^2

Q_2 = F*d^2 / [ko*Q_1] = 7.2 N * (0.2m)^2 / [9.0 x 10^9 N/m^2C^2 * 4.0 x 10^-6C] = 8x10^-6C = 8 microC

Julia would be observing a. static electricity was caused by her sweater rubbing against her shirt and transferring electrons. she didn't touch anything metal, so that would cancel out b.she most likely didn't rub her sweater against her hair either, so that cancels out c.she also didn't scoot across the carpet while trying to take her sweater off, that cancels out d.so that leaves a.a. is correct.