Here are two ways to do it:
Way #1:
-- You know that gravity accelerates things that are falling freely, adding 9.8 m/s to their speed every second.
-- After 6 seconds, an object that fell from rest winds up falling at (9.8 x 6) = 58.8m/s.
-- During that time, its average speed was 1/2(0 + 58.8) = 29.4 m/s .
-- In 6 seconds, at an average speed of 29.4 m/s, it covers (29.4 x 6) = 176.4meters.
Way #2:
This way only works if you remember the formula for the distance covered during uniform acceleration.
D = 1/2 (acceleration) (time)²
Acceleration = gravity = 9.8 m/s²
Time = 6 seconds
D = 1/2 (9.8) (6)² = 176.4 meters.
