When a book and a crumpled piece of paper are dropped from the same height, why do they hit the ground at the same time?

The correct choice indicates that air resistance is negligible for both objects, which is crucial to understanding why they hit the ground at the same time. In a vacuum, where there is no air resistance, all objects fall at the same rate regardless of their mass or shape due to the uniform acceleration of gravity.

In this scenario, while in the presence of air, the crumpled piece of paper typically experiences more air resistance than the book because of its larger surface area relative to its weight. However, if we assume conditions where air resistance is negligible for both objects—usually when dropped from a low height or in a situation where the effects of air are minimal—they will accelerate at the same rate and thus hit the ground simultaneously.

Options suggesting weight, initial speed, or the material composition do not account for the fundamental physical principles governing free fall applications of gravity in an environment where air drag significantly influences the motion of objects. Thus, recognizing that minimal air resistance allows both objects to fall at the same rate leads us to the correct conclusion.