Since I'm new member of this forum, I assume that my respnse
is not so actual.
However , I want is to make something clear:
According to what has been wriiten before, under the assumption that
the balls don't bump into each other in their way to the ground and the air resistance is neglectable, they will reach to the ground at the same time.
According to Newton law of motion, the gravitation force that
is activated on the balls depends on their mass only, and its value is mg.
(m is the mass of each ball, g is constnt and equals to 9.81m/sqrsec approxim.)
It does not matter the height each ball is dropped from.
However the time it takes to each one of them to reach to the ground depends
on the height they are dropped from, and its value is (2gh)^0.5.(h is the height where the bals are located at the beginning, g is constnt). So according to this formula, if they are dropped from the same height, the time it takes is the same to each one of them.
If we drop a feather and a heavy body in vacuum from the same height,
they'll reach to the ground in the same time, although there is a difference
between the weights. In real life, the heavy body reaches first due to
air resistance that delays the feather