Suppose Galileo dropped a one-kilogram ball of cotton and one-kilogram ball of iron from the top of the Leaning Tower of Pisa, then which one will reach the ground first? Assume that the cotton ball is tightly wadded up and that initially the bottoms of the cotton ball and iron ball are at the same horizontal level. source
The answer to this question apparently is the iron ball, but I don't see any reason why that'd be, considering that they have equal masses! Does density affect the rate at which an object falls?