This is a very well known problem, but I can't find an answer in the specific case I'm looking for.
Let's consider two balls :
- Ball 1 weighs 10 kg
- Ball 2 weighs 1 kg
- Balls have identical volumes (so Ball 1 is much more dense)
- Balls have identical shapes (perfect spheres)
Let's drop them from a rather important height, on earth, WITH air. (That's the important thing, because all the proofs that I browse take place in a vaccum).
I am arguing with a colleague. He thinks that ball 1 will fall faster in air, and that the two balls will fall at the same speed in a vacuum. I think that the identical shapes and volumes make air friction identical too and that the vaccum has no importance here. Could someone tell who's right and provide a small proof?