Competency #1

Answer and Explanation

The correct answer is C.

Lets look at our choices:

  1. The smaller object on the moon. There is no air on the moon (and thus no air resistance), so no object, big or small, could ever reach terminal velocity on the moon.
  2. Air resistance depends on cross-sectional area and speed. A small object will experience less air resistance than a large object. Since the smaller object has less cross-sectional area, it will need to achieve a greater speed than the larger object to reach terminal velocity.
  3. Since air resistance will be greater for the larger object (at equal speeds), this object will reach terminal velocity first. This means that the smaller object will continue to accelerate after the larger object has reached terminal velocity. The smaller object will reach the ground first (assuming the fall is far enough for air resistance to become a factor).

An example of two objects with equal mass, but different size is a crumpled piece of paper and a flat sheet of paper dropped horizontally. The flat sheet of paper will reach terminal velocity quite quickly, while the crumpled paper continues to accelerate.

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