If you drop an object from a great height with no air resistance. e.g. 1000 km above the moon. How long will it take to hit the surface?
(GM_{}1M_{}2)/r^{}2 = M_{}2a
r^{}..=k/r^{}2
Hmm this is my first post, not quite getting the symbols.
"The second derivative of r is equal to a...