Adoor 1.00 m wide, of mass 15 kg, is hinged at one side so that it can rotate without friction about a vertical axis. it is unlatched. a police officer fires a bullet with a mass of 10 g and a speed of 400 m/s into the exact center of the door, in a direction perpendicular to the plane of the door. find the angular speed of the door just after the bullet embeds itself in the door. is kinetic energy conserved? show calculations to justify your answer.