At a time when mining asteroids has become feasible, astronauts have connected a line between their 600 kg space ship and a 1200 kg asteroid. Using their ship's engine, they pull on the asteroid with a constant force of 450 N. Initially the space ship and the asteroid are at rest, 225m apart. How much time (in second) does it take for the ship and the asteroid to meet? (Neglect gravitational interaction).