If k is the average height of irregularities and δ is the thickness of the laminar sub-layer, then the boundary is known to be hydrodynamically rough when _______.

Which of the following dimensionless numbers represents the ratio of inertial force to surface tension force?

Determine PA - PB (in Pascal) for an inverted U-tube differential manometer measuring two pressure points. Specific weight of water = 9810 N/m3, specific gravity of Hg = 13.6, and g = 9.81 m/s2.