At the same moment, one rock is dropped and one is thrown downward with an initial velocity of 10m/s from the top of a 300m building. How much earlier does the thrown rock strike the ground? (Disregard air resistance)

i think the answer is a, hope this : )

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.