87) In a short cylindrical external mouthpiece, the vena contracta occurs at a distance __________ the diameter of the orifice from the outlet of orifice.

88) Viscous force is the __________ of shear stress due to viscosity and cross-sectionar area of flow.

89) The density of air is same at different heights.

90) The total pressure on a horizontally immersed surface is (where w = Specific weight of the liquid, A = Area of the immersed surface, and x = Depth of the centre of gravity of the immersed surface from the liquid surf

91) A body floating in a liquid is said to be in a stable equilibrium, if its metacentre coincides with its centre of gravity.