A1250 kg car is stopped at a traffic light. a 3550 kg truck moving at 8.33 m/s hits the car from behind. if bumpers lock, how fast will the two vehicles move?

i think the answer is b

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.