Two objects collide and stick together. Object A (2 kg, 6 m/s) hits stationary Object B (4 kg). What is their combined velocity after the collision?

CONSERVATION OF MOMENTUM (perfectly inelastic collision): Total momentum before = Total momentum after. Momentum = mass × velocity. Before: Object A: 2 kg × 6 m/s = 12 kg·m/s; Object B: 4 kg × 0 = 0. Total before: 12 kg·m/s. After: Combined mass = 2 + 4 = 6 kg. 6 kg × v = 12 kg·m/s. v = 12 ÷ 6 = 2 m/s. Note: kinetic energy is NOT conserved in inelastic collisions (some becomes heat/sound/deformation). Momentum IS always conserved in all collisions.