14. Sets of objects made of various materials undergo head-on collisions. Each set consists of two masses (m] = 2.0 kg and m, = 4.0 kg). Given the following initial and final velocities, identify the collisions as elastic, inelastic, or completely inelastic. (a) vji = 6.0 m/s; v2; = 0; VIf V2f = 2.0 m/s (b) via = 24 m/s; v2; = 0; VIf --4.0 m/s; V26 = 14 m/s (c) vij = 12 m/s; v2; = 0; VIf= -4.0 m/s; V2f = 8.0 m/s