Three point charges, two positive and one negative, each having a msgnitude of 20 ¡ are placed at the vertices of an equilateral triangle (30 cm on a side). what is tihe magnitude of the electrostatie force on the negative charge? a. 57n b. 40 n d. 80 n e. 75 n c. 69 ns 15. a point charge q is placed at the origin. a second charge, 20, is placed on the x axis at x--3.0 m-10-50 c, what is the magnitude of the electrostatic force on a third point charge, -q, placed on the y axcis at y- +4.0 m? a. 4.4n b. 1.8 n d. 2.5 n e. 3.7 n e. 3.0n