Cousin to an Elephant Whose Mass May Be Ignored

Figuring otu when ignoring air resistance is a bad approximation.

When Does the Air Resistance Force Make a Difference?

With only the gravitational force, the object has a constant acceleration and the motion is fairly simple to model.

However, objects on the surface of the Earth usually have an air resistance force on them also. When can we ignore this extra force and when is it important?