Final answer:
The times spent falling by the ball thrown horizontally and the ball dropped straight down are the same.
Step-by-step explanation:
The times spent falling by the ball thrown horizontally and the ball dropped straight down are the same. The vertical motion of a falling object is independent of its horizontal motion, assuming no air resistance. The horizontal velocity of the thrown ball does not affect the time it takes to fall vertically, as long as there are no additional horizontal forces acting on it after it is thrown.