What are the differences in the level and kind of preparedness for calculus typically found in students beginning a calculus course at a university in the USA today, and those beginning such a course between five and eight years ago?
Later note: I've taught first-semester calculus during most semesters during that time period. I notice an answer that says "My personal feeling is that[...]" this or that would happen instead of "I have observed in teaching calculus eash semester during that time that[...]" this or that would happen. (Nonetheless there was something of value elsewhere in the answer).
I've noticed a change toward more students never having heard that math doesn't just consist of memorizing algorithms, and I've heard from someone claiming to have been watching closely that students are rapidly getting less well-prepared BUT these are based on small samples, and the variation from one class of about 25 students to another, merely because it's a difference group of 25 students, actually is quite large. That is to be expected when you consider that $\sqrt{25}=5$, so the SD of the sample mean should be about $1/5$ of the SD that you'd consider if you're thinking about variation from one individual student to the next.
Another later note: Answers that don't stray too far from empirical observation are better than those that say that the heavier rock would fall faster than the lighter one.