A sample of a viscous fluid is tested in a cup-and-bob viscometer that has a cup radius of 2.1 cm, a bob radius of 2.0 cm, and a bob length of 5 cm. When the cup is rotated at 10 rpm, the torque measured at the bob is 6000dyn cm, and at 100 rpm the torque is 15,000 dyn cm.
(a) What is the viscosity of this sample?
(b) What can you conclude about the viscous properties of the sample?
(c) If the cup is rotated at 500 rpm, what will be the torque on the bob and the fluid viscosity? Clearly explain any assumptions you make to answer this question, and tell how you might check the validity of these assumptions.
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