Final answer:
A visgauge is used to measure the viscosity of liquids by observing the time it takes for a steel ball to fall through the liquid and using Stokes' law to calculate the viscosity, which is important for quality control and ensuring proper liquid performance.
Step-by-step explanation:
You would use a visgauge or field viscosity check tool to measure the viscosity of liquids in practical situations, such as in engineering or quality control processes. Viscosity is fundamentally the resistance of a liquid to flow. The greater the viscosity, the more slowly a liquid flows. In a common test, you drop a steel ball through the liquid and measure how long it takes to fall a certain distance. From this, using Stokes' law, you can determine the liquid's viscosity. For example, if a steel ball bearing with a density of 7.8 x 10³ kg/m³ and a diameter of 3.0 mm is dropped in motor oil and takes 12 seconds to fall 0.60 meters, you can calculate the motor oil's viscosity. This kind of testing is crucial for ensuring that liquids like motor oil perform correctly under various conditions.