Debating with physics teacher.

[Michael Hill]

I agree...poorly worded. It really should say something about assuming they're the same shape of the same size. I read "air resistance" from a force perspective (coming from an aeronautics background). So if they're the same size and shape, the heavy rock will experience more force. You can assume they're spheres if you want (it turns out the specific shape doesn't really matter). The aerodynamic force on a sphere will be a function of shape, surface finish, and velocity. See this: https://www.grc.nasa.gov/www/K-12/ai...ragsphere.html

Because the heavier rock has a greater gravitational force, it needs a greater aerodynamic force to counteract the gravitational force (at terminal velocity). Since the aerodynamic force is greater, the velocity is greater (this is why heavier objects of the same shape have a higher terminal velocity). Since the aerodynamic force is greater, it experiences more air resistance.