Two 40-Kg Blocks Are Tied Together with a Compressed Spring Between

Multiple Choice

Two 4.0-kg blocks are tied together with a compressed spring between them.They are thrown from the ground with an initial velocity of 35 m/s, 45° above the horizontal.At the highest point of the trajectory they become untied and spring apart.About how far below the highest point is the center of mass of the two-block system 2.0 s later, before either fragment has hit the ground?

A) 1.2 m
B) 20 m
C) 31 m
D) Can't tell because the velocities of the fragments are not given.
E) Can't tell because the coordinates of the highest point are not given.