you are in a rocket ship in deep space, far away from any gravity. you decide to do an experiment to determine the mass of your rocket ship. initially your ship is traveling to the right at 800 m/s, then the engines begin to exert 300,000 n of constant force to the left and do so for 40 seconds. afterward, your rocket ship is traveling to the left at 200 m/s. what is the mass of your rocket ship?