Question

A ball rolls off the edge of a horizontal roof at 10 m/s. 2 seconds later, what will be its horizontal speed?

Answer 1

horizontal speed and vertical speed when falling have no effect on each other. If the ball is moving at 10m/s horizontally at one instant of time, it will not change its horiztonal velocity at any time during its fall (until it hits the ground). That's why falling objects follow a parabolic path, not a straight one.