Complete Solution Questions: These problems are to be answered with detailed calculations. Problem 3. Find the electrostatic force on charge q (Fig. 1). 0.10 m 0.10 m q = +12 q = +12 93 = -12 C Figure 1: Problem 7: Find the electrostatic force on charge q1. Problem 4. Three negative charges of equal magnitude q are placed along a straight line, the first and second charges a distance r apart and the second and third charges also a distance r apart. (a) Find the electrostatic force on the middle (second) charge. (b) If you move the middle charge a distance r along the perpendicular passing trough the middle point between the two end charges (see Fig. 2) will the electrostatic force on it change? If it does, find the new one, if it does not, explain why not. Figure 2: Position of the charges after moving the middle one. Conceptual Questions: These questions are to be answered with a short para- graph. Problem 1. Object A is positively charged. It repels object B. What conclusion can you make about object B: (a) It is negatively charged. (b) It is positively charged. (c) It is not charged. (d) It is either negatively charged or not charged. (e) It is either positively charged or not charged. Problem 2. You have two positive charges some distance apart. You want to add a third charge in such a way as to keep the system in equilibrium. What should the sign of that third charge be? Draw a possible configuration of the three charges in equilibrium. Problem 5. Four equal point charges q = +10 nC are placed at the four corners of a square with side a = 10 cm. Find the force that any three of them are exercising on the forth.