1. Three point charges are placed in such a way that their coordinates are (0, a), (0, -a) cos (a, 0). Calculate the electrostatic force acting on the point charge placed on X axis. 2. Point charge is placed at the origin. Three point charges . have the following coordinates (a, 0), (a, a) and (0, a). Calculate the electrostatic force acting on the point charge placed at the origin of coordinates. 3. Three point charges +q are placed on the circle of radius /" (center of the circle is at the origin of coordinates) and their corresponding angles are 30 150* and 270 . Find the resultant electric field at the center of the circle. 4. Two beads with electric charge are suspended from one point by the strings of equal length / . The beads have equal mass M . The angle of the strings with respect to vertical is . Assume, that electric charge of the beads is known and calculate their mass