At a certain section in a pipeline, a reducer is used to reduce the diameter from 2D gradually to diameter D. When an incompressible fluid flows through this pipeline, the velocity is U1 in the first section and U2 in the second section. Which of the following is a true conclusion?

Awater-filled u-tube manometer is used to measure the pressure inside a tank that contains air. the water level in the u-tube on the side that connects to the tank is 5 ft above the base of the tank. the water level in the other side of the u-tube (which is open to the atmosphere) is 2 ft above the base. determine the pressure within the tank.