Little Joey loves to watch trains. His dad took him to a nearby railroad track with an adjacent park. From the picnic table closest to the tracks, they could watch the train from Podunk zoom by. If the perpendicular distance from their picnic table to the tracks is 100 feet, and the train is traveling at 150 ft/sec, at how many ft/sec is the train moving away from Joey 6 seconds after it passes their picnic table?