Answer:
It would be the last one.
Step-by-step explanation:
It says the object is initially at rest, so you look for a table with 0 m/s and you find the last table had been at rest for 0 -2 seconds. The small rocky object initially had a speed of 90 m/s and then decreased to 36 m/s as its energy transferred to the metallic object. The metallic object's speed from time 4-6s with the small rocky object equals the small rocky initial speed.
Rocky Object initial speed = 90 m/s
Rocky Object new speed = 36 m/s
Large metallic object speed after collision = 64 m/s.
64 m/s + 36 m/s = 90 m/s
Large metallic object speed after collision + Rocky Object new speed
= Rocky Object initial speed
You can also test this for kinetic energy.
