Asolid steel disc has an outer diameter of 500mm and a constant thickness of 25mm. the disc has 110 steel blades equi-spaced around its outer edge. each blade has a cross-sectional area of 60mm2. the disc is rotating at 1200rpm and the average radial stress is 150mpa. the density of steel is 7480 kg/m3. how long are the blades to the nearest mm?

Ahe-xe mixture containing a 0.75 mole fraction of helium is used for cooling electronics in an avionics application. at a temperature of 300 k and atmospheric pressure, calculate the mass fraction of helium and the mass density, molar concentration and molecular weight of the mixture. if the cooling capacity is 10 l, what is the mass of the coolant?