the answer is attached but Im wondering how it was achieved

the answer is attached but I\'m wondering how it was achieved. Thanks!

Solution

Here

for the force between 2 nC and 1 nC

F1 = k * q1 * q2/d^2

F1 = 9 *10^9 * 2 *10^-9 * 1 *10^-9/.05^2

F1 = 7.2 *10^-6 N

for the force between -6 nC and 1 nC

F2 = k * q1 * q2/d^2

F2 = 9 *10^9 * 6 *10^-9 * 1 *10^-9/.05^2

F2 = 21.6 *10^-6 N

for the net force on the charge 1 nC

net force = F2 - 2 * F1 * cos(45)

net force = 21.6 *10^-6 - 2 * 7.2 *10^-6 * cos(45)

net force = 1.141 *10^-5 N

the magnitude of net force on the bottom charge is 1.141 *10^-5 N