Electric Forces and Fields: Study Notes

A charge $q_1 = -3.0 \times 10^{-6}\,\mathrm{C}$ is located at the origin, and a charge $q_2 = 5.0 \times 10^{-6}\,\mathrm{C}$ is located at $(0.040\,\mathrm{m}, 0.030\,\mathrm{m})$. What is the magnitude of the force exerted on $q_2$ by $q_1$? Use $k = 9.0 \times 10^9\,\mathrm{N\cdot m^2/C^2}$.

Given three charges: $q_1 = -3.0 \times 10^{-6}\,\mathrm{C}$ at the origin, $q_2 = 5.0 \times 10^{-6}\,\mathrm{C}$ at $(0.040\,\mathrm{m}, 0.030\,\mathrm{m})$, and $q_3 = 3.0 \times 10^{-6}\,\mathrm{C}$ at $(0, 0.030\,\mathrm{m})$, what is the magnitude of the net force on $q_2$ due to $q_1$ and $q_3$?

Which of the following correctly describes the direction of the electric field created by a positive point charge?