A very small object with mass 7.80 × 10⁻⁹ kg and positive charge 6.40 × 10⁻⁹ C is projected directly toward a very large insulating sheet of positive charge that has uniform surface charge density 5.90 × 10⁻⁸ C/m². The object is initially 0.320 m from the sheet. What initial speed must the object have in order for its closest distance of approach to the sheet to be 0.120 m?