An air brick is a brick-sized block with holes embedded in a wall to allow ventilation through it.
Yes, air has a significantly lower mass than a brick. Air is made up of gases, which have a very low density compared to the solid materials that make up a brick. A typical brick weighs much more than the same volume of air.
It is the wood trim that the brick stops behind or against. It hides the top or end of brick so you don't see the air space behind the brick.
Water
because of air resistance
It is slowed down by air resistance.because feather's weight is negligible as compare to force of gravityA feather will fall through the air more slowly than a brick because it is lighter than a brick and it's small fur on it will slow it down
That depends on the volume of the brick. Whatever its volume is, its weight underwater is(weight of the brick in air) minus (weight of an equal volume of water)
If you dropped them in a vacuum, they would fall at the same rate. However, when you do it in air, the friction from the air will slow the feather considerably, as the surface area to mass is much greater then that of the brick.
because feather's weight is negligible as compare to force of gravityA feather will fall through the air more slowly than a brick because it is lighter than a brick and it's small fur on it will slow it down
The weight of the displaced water is 2/3 the weight of the brick. So the weight of the brick is 3/2 the weight of an equal volume of water ... just another way of saying that the density of the brick is 1.5 gm/cm3.
A feather falls slower than a brick because of air resistance. The larger surface area of the feather allows more air resistance to act against it, slowing down its fall. The brick is denser and has a smaller surface area, so it falls faster due to less air resistance.
The resistance of the air.
gravity