The force of gravity on a 2kg is twice as great as that on 1kg rock.?

Question

why then does not the heavier rock fall faster ?

Answer 1

To make sure that the 2kg rock falls at the same rate as the 1k rock the force on each rock must be "tweaked" to make them fall at the same speed.

To make a 2kg rock accelerate at the same rate as a 1kg rock,  you need to apply more force to it (since mass aka kilograms aka inertia means resistance to accelerate).

In other words, to achieve the same result, you have to apply more force for the rock that needs more "boost".

======UPATE======

TOTALLY GIVE RICKB THE BEST ANSWER.  HE NEEDS 60 MORE BEST ANSWERS AND HE BECOMES A *TOP*CONTRIBUTOR*  

If you like my answer give it a +1 thumbs up, but Rick B totally needs it.  Thanks and god bless.  I pray you'll make his dream come true.

Answer 2

Because the heavier rock also has twice as much inertia (resistance to change).

If something has a larger mass, it requires a larger force to get it going.  When you double the mass of something, you double the amount by which the earth pulls it, but you also double the amount by which it _resists_ the earth's pull.  The two effects exactly cancel each other out, so the end result is that the rate at which it falls is the same as a smaller rock.