Let’s assume that we can ignore the resistance of the air (as one usual does in physics homework).
The distance ‘s’ traveled by an object under constant acceleration ‘a’ in a time ‘t’ is given by
s = 1/2 a t^2
if the object starts at rest. As t=4 seconds and ‘a’ is the usual 9.81 m/s^2, you can put the numbers in and get
s=8*9.81 m ~78.5m or 78 500 cm
A foot amounts to (as you know) 30.3 cm, so you have to divide the above number by the 30.3cm/ft and get
s ~ 257 ft.
Explanation:
