A500 kg train car(car1) is traveling at 25 meters per second when it hits and attaches to another 750 kg train car(car2) that is at rest. find the resulting velocity of both train cars after they hit and the momentum of the train cars before and after they attached

the answer is a)

mark brainliest

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me