(Solved): 2. ( 20 pts) A cup and bob geometry is filled with a fluid, and the bob rotates at a rate of =1 H ...

2. ( 20 pts) A cup and bob geometry is filled with a fluid, and the bob rotates at a rate of $?=1$ $\mathrm{Hz}(\mathrm{Hz}$, or hertz, has unit of \# rotations per second). The bob has a radius of $R=1\mathrm{cm}$. (a) (5 pts) What is the velocity of the bob at point $P$ on the surface of the bob in $\mathrm{m}/\mathrm{s}$ ? (b) $(5$ pts) What is the velocity of the fluid touching point $P$ on the bob in $\mathrm{m}/\mathrm{s}$ ? (c) (5 pts) Why can we be confident of our answer to part (b)? (d) (5 pts) What type of stress (shear, normal, or both) does the bob have to exert on the fluid in order to rotate?