Here is an experiment to try. Take your jet up to 350 feet and nose her over until she is going straight down, Adjust throttle and flight controls so that she is travelling straight down with all forces being equal. Clearly she has momentum with repsect to the ground. But just as clearly she has NO momentum with respect to the leading edge of the wing. Keep her pointed straight down and when when smacks into the gound tell me that momentum with respect to the ground doesn't matter.
