Problem 1: Center of Mass At t1=0, a 1.0 kg box is projected vertically upward from the base of a 50-m-tall building with an initial velocity of 40 m/s. At the same instant and directly overhead, a 2.0 kg box is dropped from rest from the top of the building. How far above ground level is the center of mass of the two-box system at t2=3.0s?