For these devices and for blood pressure machines, the units are often millimeters of mercury rather than Pascals.
ARCHIMEDES PRINCIPLE This topic gets into the idea that some things are buoyant and others are not. Buoyancy involves things being able to float in water as well as things floating in air, such as helium balloons. If the buoyant force is greater than the object’s weight, the object will rise; likewise, if the weight is greater than its buoyancy, the object will sink. The buoyant force is the net upward force on any object within a fluid. This will be the difference between the upward force and the downward force. According to Archimedes principle, the buoyant force on an object equals the weight of the fluid it displaces. This is valid, whether the object is partially or completely submerged. Boats will float because of their shape. They will displace more water, experiencing a greater buoyant force. It turns out that you can calculate the buoyant force on an object. Figure 61 shows the buoyant force of an object according to Archimedes principle:
Figure 61.
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