Why have modern vacuums dispensed with the lowhole at the back of the machine?
Over time, vacuum cleaners have evolved to include supplementary mechanisms that assist in the process of cleaning with vacuum force. Modern household floor vacuum cleaners usually still have a detachable hose, but now also use a system of dust rollers (equipped with rows of brushes) and wheels in the base of the cleaner. As the cleaner is pushed across the floor on its wheels, the rollers sweep up dust and debris in the carpet or on the floor and deposit it into the air beneath the base of the vacuum, making it easier for this sediment to be picked up by the nearby end of the vacuum hose. The foundational technology of a vacuum cleaner is the air pump, such as the one pictured here. With this pump, a hand-operated plunger is attached to an airtight space. When pulled out, the volume of the enclosed space increases, but no air molecules are able to flow into it. This creates a less-dense space inside the sealed area, causing a partial vacuum. If a closed tube is attached to this sealed
