1. The problem statement, all variables and given/known data A ball is traveling horizontally over a volleyball net when a player "spikes" it, driving it straight down to the ground. The ball's mass is 0.20 kg, its speed before being hit is 6.4 m/s and its speed immediately after the spike is 21 m/s. What is the magnitude of the impulse from the spike? 2. Relevant equations J=mv(final)-mv(initial) 3. The attempt at a solution J=.20(0,-21)-.20(6.4,0) J=(0,-4.2)-(1.28,0) J=(1.28,-4.2) I don't understand where I went wrong, but the book tells me that this is incorrect.