question_answer

    If energy in the universe is constant, why is the world yelling out for energy crisis? What does judicious use of energy imply?

Answer:

                  (a) Windmill works on the principle of conversion of wind energy into kinetic energy of blades of windmill which can be used to do useful work.                                                              (2) (b) 15 km/h is the minimum wind velocity required to obtain energy.                           (1/2) (c) Wind does not blow at sufficiently high speed all the time.                                         (1/2)