This demo serves to show the dependence of the buoyant force on the floating medium's density for a given mass. It consists of a boat of a mass and volume such that the edge of the boat is barely touching the surface of the water when it's floating – that is, such that it's almost about to sink. This boat is placed on an acrylic cylinder that has aerators at the bottom and that can be filled with water. When filled with water, the boat barely floats. Injecting air through the aerators generates many small bubbles in the water, causing the density of the water to decrease. This causes the buoyant force to decrease and the boat to slightly sink. The edge of the boat will now be submerged, which will cause water to fill the boat and sink it.

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