What happens when you increase the horizontal velocity to the maximum?

If a stone with an original velocity of 0 is falling from a ledgeand takes 8 seconds to hoybthe ground whays the final velocity of the stone

Considering only the earth's rotation, determine how much later the asteroid would have had to arrive to put the explosion above helsinki at longitude 25˚ e? this would have obliterated the city.

This is for my 8th grade science class, i really don’t understand. can someone me? , lol.