Well, it's because the air offers much greater resistance to the falling motion of the feather than it does to the brick. The air is actually an upward force of friction, acting against gravity and slowing down the rate at which the feather falls. read more
For the feather a is going to reach 9.8 at much lower velocitys than the rock. So the rock will over all obtain a much higher velocity and fall faster. read more
Scott dropped a feather and hammer and watched as they fell in the same time, proving that all objects fall at the same rate when air resistance and other forces do not come into play. To create an air-free environment, similar to the conditions encountered in space, the Nasa vacuum chamber is able to pump out 30 tons of air until there are just two grams (0.004lbs) left. read more