A liquid (viscosity = 0.002 N . s/m2; density = 1000 kg/m3) is forced through the circul...

A liquid (viscosity = 0.002 N . s/m2; density = 1000 kg/m3) is forced through the circular tube shown in Fig. P6.81. A differential manometer is connected to the tube as shown to measure the pressure drop along the tube. When the differential reading, , is 9 mm, what is the mean velocity in the tube?