At the instant a ball is thrown horizontally over a level range, a ball held at the side of the first is...?

Question

At the instant a ball is thrown horizontally over a level range, a ball held at the side of the first is released and drops to the ground. If air resistance can be neglected, which ball- the one -thrown or the one dropped from rest- strikes the ground first?

When you answer the question, please also explain WHY, because I don’t just want the answer, I want to learn also =)

Answer 1

They strike the ground at the same time. The same force of gravity is acting on both balls. Since both balls started falling (from the force of gravity) from the same height, they will fall towards the ground with the same acceleration. Consequently, they hit the ground at the same time. The fact that one ball has horizontal motion has nothing to do with its 'vertical' motion.