Final answer:
All balls launched with the same speed from the same height and one dropped will hit the ground simultaneously due to the independence of vertical motion from horizontal motion in projectile dynamics.
Step-by-step explanation:
The question involves understanding the principles of projectile motion and the independence of vertical and horizontal components of motion in physics. When multiple balls are launched with the same speed from the same height, and one is simply dropped, we can assume that all the balls will hit the ground at the same time, provided air resistance is negligible. This is because the time taken to hit the ground only depends on the initial vertical position and the acceleration due to gravity, not on the horizontal or vertical components of the initial velocity. Therefore, if balls 1 through 4 are launched (vertically, horizontally, or at an angle) and ball 5 is dropped, all will land at the same time, assuming they all start from the same height. To test the hypothesis that acceleration is independent of the initial velocity, the student would need to collect data on the time it takes each ball to hit the ground (time of flight), as well as their respective heights and initial velocities if needed.