A6630 kg train car moving at positive 2.0 m/s bumps into an locks together with one of mass 5400 kg moving at -3.0 m/s. what is the final velocity?

Point charges q1 = 51 µc and q2 = −27 µc are placed 1.0 m apart, with q2 on the right. what is the force (in n) on a third charge q3 = 19 µc placed midway between q1 and q2? (assume the positive direction is to the right. indicate the direction with the sign of your answer.)