to measure the mass of an object, the object and a fixed 1.00 kg mass are held at rest on a frictionless surface with a llight spring under compression between the two objects. the system is then release; the 1.00 kg mass moves away from the"explosion" with a speed of 3.20 m/s, and the unknown mass moves in the opposite direction with a speed of 1.70 m/s. what is the mass of the object?