Final answer:
The unit of time used to measure viscosity in the provided context is seconds. Viscosity measures a fluid's resistance to flow and can be calculated by observing how long it takes an object to move through the fluid, using principles such as Stokes' law. The viscosity is the time in seconds for 60 cm3 of oil to run through an orifice, at 38°C. Thus, the correct answer to the student's question is b. seconds.
Step-by-step explanation:
The viscosity is the time in seconds for 60 cm3 of oil to run through an orifice, at 38°C. Thus, the correct answer to the student's question is b. seconds. Viscosity (η) is a measure of a fluid's resistance to flow. It plays a critical role in fluid dynamics and can be quantified by observing how quickly objects move through the substance, such as a steel ball bearing through oil.
In the example given, where a steel ball bearing with a density of 7.8 x 10³ kg/m³ and a diameter of 3.0 mm is dropped in a container of motor oil, the time of 12 seconds it takes to fall 0.60 meters can be used to calculate the viscosity of the oil. This calculation would typically involve equations derived from Stokes' law, which allows the determination of the drag force and consequently the viscosity when the terminal velocity is reached.