Three charges lie on a line: q1 = +2.0 nC on the left, q2 = +5.0 nC in the middle, and q3 = -3.0 nC on the right. Both q1 and q3 sit 2.0 cm from q2. What is the net electric force on the middle charge q2?

1. Charge q1 is positive and pushes q2 away from itself, which points toward the right, with size k q1 q2 / r^2 = (8.99 x 10^9)(2.0 x 10^-9)(5.0 x 10^-9) / (0.020)^2 = 2.25 x 10^-4 N. 2. Charge q3 is negative and pulls q2 toward itself, which also points toward the right, with size k |q3| q2 / r^2 = (8.99 x 10^9)(3.0 x 10^-9)(5.0 x 10^-9) / (0.020)^2 = 3.37 x 10^-4 N. 3. Both contributions point the same way, toward the right, so they add rather than cancel: 2.25 x 10^-4 N + 3.37 x 10^-4 N = 5.6 x 10^-4 N. 4. The trap is assuming a positive charge on one side and a negative charge on the other must pull the middle charge in opposite directions; here both a push from q1 and a pull from q3 act toward the same side. _Source: OpenStax Physics (CC BY 4.0), Ch 18 "Static Electricity", section 18.2 Coulomb's law_