Answer:
16.67 m/s
Step-by-step explanation:
Let that velocity be v.
Using conservation of momentum:
Initial momentum = final momentum
momentum of car1 = momentum of cars
mass1 x velocity1 = (m1 + m2)v
1500*30 = (1500 + 1200)v
45000/2700 = v
16.67 m/s = v