6. An incompressible non-viscous fluid (density ) flows steadily through a cylindrical pipe which has radius 2R at point A and radius R at point B (at the same height as A) further along the flow direction. If the velocity and pressure at point A are v and P, respectively, find the pressure at B.
7. A cylindrical vessel filled with water upto a height of 2 m stands on a horizontal plane. The side wall of the vessel is a plugged circular hole touching the bottom. Find the minimum diameter of the hole so that the vessel begins to move on the floor if the plug is remove. The coefficient of friction between the bottom of the vessel and the plane is 0.4 and total mass of water plus vessel is 100 kg.