What is the reason for the small air resistance when a dense object falls (in the experiment to verify the law of conservation of mechanical energy)?

What is the reason for the small air resistance when a dense object falls (in the experiment to verify the law of conservation of mechanical energy)?

The same volume of the object density is large, the volume is small, when moving in the air, the resistance of the air is small, the influence on the movement is small. The experimental error is small. So we choose the object with high density, such as iron ball