$1\mathrm{.}6\mathrm{.}25$ The concentric cylinder viscometer shown in Fig. P$1\mathrm{.}6\mathrm{.}25$

has a cylinder height of $10\mathrm{.}0$ cm $,$ a cylinder radius of $3\mathrm{.}0$ cm $,$ and a uni$-$

form gap between the cylinder and the container $($bottom and sides$)$

of $0\mathrm{.}10$ cm $.$ The pulley has a radius of $3\mathrm{.}0$ cm $.$ Determine the weight

required to produce a constant rotational speed of $30$ rpm if the gap is

filled with: $($a$)$ water, $($b$)$ gasoline, and $($c$)$ glycerin.