17. A small object of mass 3.80 g and charge -18.0 C is suspended motionless above the ground when immersed in a uniform electric field perpendicular to the ground. What is the magnitude and direction of the electric field? Answer 2.07 103 N/C down 18. a. Determine the electric field strength at a point 1.00 cm to the left of the middle charge shown in Figure P15.10. b. If a charge of -2.00 C is placed at this point, what are the magnitude and direction of the force on it?