Physics Work,Power & Energy Level: Misc Level

Near the surface of the Earth there is an electric field of about 150 V/m which points downward. Two identical balls with mass m=0.540 kg are dropped from a height of 2.0 m, but one of the balls is positively charged with q1=+550 microCoulombs and the second is negatively charged with q2=-550 microCoulombs. Use conservation of energy to determine the difference in the speed of the two balls when they hit the ground. (neglect air resistance)