Distance varies directly with square of time.
D = Kt2
in 4 seconds it falls 128'
Use this to solve for k
128 = k(4)2
128 = 16k
k = 8
Using this value of k, the equation becomes
D = 8t2
In 2 seconds
D = 8(2)2
D = 8 (4) = 32
The object falls 32 feet in 2 seconds.