Just to be a smartass, I'd like to refute your statement about the feather and bowling ball. Your teacher is right. If both are dropped in a vacuum, that is, under the same gravity. The reason the feather doesn't drop as fast is because it has a higher surface area to mass ratio, and consequently, higher drag.
The proof for this is that acceleration due to gravity is constant for all objects (9.?? ft / sec.) I bet if you dropped me and a two ton block of led from a highrise, we'd both go splat at the same time. Not to give YOU any ideas of course!