A two-blade wind turbine is installed on top of a hill experiencing winds of up to 80 mile/h….

A two-blade wind turbine is installed on top of a hill
experiencing winds of up to 80 mile/h. Downstream of the propeller the wind
speed is 50 mile/h. Assume ideal gas and standard condition for air and find
the tip to tip diameter of the propeller to obtain a theoretical efficiency of
50%.