I am having some trouble with these question. can you please provide an explanation?

10 . . Three point charges, +9 +q, +Q, and -Q, are placed at the corners of an equilateral tri- angle as shown in Figure 21-33. No other charged objects are To uh nearby. (a) What is the direc- tion of the net force on charge +q due to the other two charges? (b) What is the total electric force on the system of three charges? Explain.W +Q 11 .A positively charged -Q particle is free to move in a FIGURE 21-33 Problem 10 region with a nonzero electric field E. Which statement(s) must be true? (a) The particle is accelerating in the direction perpendicular to E. (b) The particle is accelerating in the direction of E. (c) The particle is moving in the direction of E. (d) The particle could be momentarily at rest. (e) The force on the particle is opposite the direction of E. (f) The particle is moving opposite the direction of E. 12 .. Four charges are fixed in place at the corners -9 + + 9 of a square as shown in Figure 21-34. No other charges are nearby. Which of the following statements is true? (a) E is zero at the midpoints of all four sides of the square. (b) E is zero at the center of - 9 the square. (c) E is zero midway between FIGURE 21 -34 Problem 12 the top two charges and midway between the bottom two charges