Can you solve these physics riddles? ft Simone Giertz - Part 1/3

I still don't understand the screw thing, surely you could make a bike without any screws. Also I don't understand if the screw is in the pedal wouldn't the screw eventually tighten and make the pedal unmovable or loosen until the pedal falls off.

but the actual question is a lot simpler, its fairly obvious that the heavier ball would go faster at terminal velocity resulting in more molecules hitting it per second resulting in higher air resistance.