Air resistance is the force that opposes the motion of an object through the air. It depends on the object's shape, size, density, and velocity. The greater the air resistance, the slower the object will fall.
For example, a feather has a large surface area and a low density, so it experiences a lot of air resistance. This causes it to fall slowly. A rock, on the other hand, has a small surface area and a high density, so it experiences less air resistance. This causes it to fall faster.
Two objects with the same mass but different shapes will experience different amounts of air resistance. The object with the larger surface area will experience more air resistance and will therefore fall slower.
In a vacuum, where there is no air resistance, all objects would fall at the same speed regardless of their mass. This is because the only force acting on the objects is gravity, which is the same for all objects with mass.
