A type of level indicator incorporates four hemispherical cups with open fronts mounted as...

A type of level indicator incorporates four hemispherical cups with open fronts mounted as shown in Fig. 17.13. Each cup is 25 mm in diameter. A motor drives the cups at a constant rotational speed. Calculate the torque that the motor must produce to maintain the motion at 20 rpm when the cups are in (a) air at 30°C and (b) gasoline at 20°C.

FIGURE 17.13