What are combined vectors that go in one direction?

Two vectors are equal if they have the same magnitude and direction. They are parallel if they have the same or opposite direction. We can combine vectors by adding them, the sum of two vectors is called the resultant.

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.