Rob and his sister Joan are standing on their apartment balcony. Rob throws a ball straight out from the balcony. At the same time, Joan drops a ball straight down. Both balls reach the ground at the same time. Which factor causes the two balls to reach the ground at the same time?

Question

Vocaloid · Answer

I couldn’t find any answer choices for this question. Notice how there is no net force* besides gravity in the vertical direction and they both start off with a vertical velocity of 0. Same staring velocity, same applied force, same vertical distance, same change in velocity, etc. so the balls end up in the same place at the same time.

* excluding air resistance which you typically consider negligible for these problems.