# Mechanical engineering A helicopter of mass 12 000 kg hovers at sea level homework help

1- A helicopter of mass 12,000 kg hovers at sea level with a load of 16,113 kg. The horizontal blades above the helicopter cause a 18-m-diameter air mass to move downward at an average velocity proportional to the over-head blade rotational velocity (rpm). Determine the power input in kW required to hover with the load. Take the density of atmospheric air to be 1.18 kg/m3. Assume air approaches the blades from the top through a large area with negligible velocity and air is forced by the blades to move down with a uniform velocity through an imaginary cylinder whose base is the blade span area. The elevation effects are negligible, and the frictional effects can be disregarded.

2-A pump is used to lift the water from a large reservoir to 28.7 m above at a rate of 0.0264 m3/s by a 10.4 kW pump. If the mechanical efficiency of the pump is 65.8 % determine the irreversible head loss (in meter) of the piping system. The density of water is 1000 kg/m3. The flow is steady and incompressible.

4-The impeller of a centrifugal pump has inner and outer diameters of 13 and 30 cm, respectively, and a flow rate of 0.68 m3/s at a rotational speed of 1200 rpm. The blade width of the impeller is 8 cm at the inlet and 3.5 cm at the outlet. If water enters the impeller in the radial direction and exits at an angle of 60° from the radial direction, determine the minimum powerrequirement in kW for the pump.

Textbook that can help is Fluid Mechanics Fundamentals and Applications, 3rd Edition Cengel, Yunus; Cimbala, John, McGraw Hill

Chapter 4,5 and 6.