Systems- open and closed

Question

a car with a mass of 1200 kg rolls down a hill and collides with a parked car that has a mass of 1500 kg. the first car starts at rest and travels a distance of 10m before the collision. If the angle of the incline is 10 degrees and the two cars stick together upon impact, how fast are the two cars traveling together immediately after the impact ? what are the possible systems in this example problem ?

Answer 1