A ball sails through the air with an initial velocity of 4m/s. It bounces off of a wall over 0.5 seconds and then has a velocity of -2m/s (in the opposite direction). What was the acceleration of the ball when it bounced off the wall? m/s²

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.)