Some variation of this question gets asked a lot:
We have 2 point masses, $m$ and $M$ in a perfect world separated by radius $r$. Starting from rest, they both begin to accelerate towards each other. So we have the gravitational force between them as:
$$F_g = \frac{GMm}{r^2}$$
How do we find out at what time they will collide?
There are two instances that seem to be emerging as "canonical", or at least that both seem to be the target of frequent duplicate closures:
- The Time That 2 Masses Will Collide Due To Newtonian Gravity (where the above quote comes from)
- Don't heavier objects actually fall faster because they exert their own gravity? (has more upvotes)
I think we should pick one of these (or potentially another version of this same question) to be the canonical target of duplicate closures. I would probably go ahead and pick #2 except that I happen to have the accepted answer on that question, and I wouldn't want people to think I'm doing it to accumulate reputation. Besides, there are some advantages to #1, namely that the question is more cleanly asked (IMO) and the accepted answer is much more direct.
What should we go with? #1 or #2, or another existing version of this, or write an entirely new canonical question for it?