Inertia can be a bit confusing until you see it revealed by a falling hex nut.
The object of this activity is to get the hex nut to drop into the plastic bottle. Simple enough but there will be something in the way. To accomplish the drop, you’ll need a combination of careful setup, Isaac Newton’s smarts, inertia, and gravity. Balance a plastic ring on the mouth of an empty soda bottle and place the hex nut (or similar heavy, small object) on top of the ring. Correctly remove the ring and the hex nut drops straight into the bottle.