The diagram above illustrates a simple barometer. Which distance measures the atmospheric pressure?

The diagram above illustrates a simple barometer. Which distance measures the atmospheric pressure?

Answer Details

The distance that measures atmospheric pressure in the diagram of the barometer is QR. This is because atmospheric pressure is the force exerted by the weight of air on the surface below it. In a simple barometer like this one, the atmospheric pressure pushes down on the surface of the mercury in the tube, causing it to rise up the tube. The height of the mercury column in the tube, measured from the level of the mercury in the bowl, is directly proportional to the atmospheric pressure pushing down on the surface of the mercury in the bowl. Therefore, the distance QR, which represents the height of the mercury column in the tube, is the measure of atmospheric pressure.