Question

a bread gives a boy of mass40kg an energy 21 kelojoule .if the efficiency is28%vthen the hight thstcan be climbing by him using this energy? ​

Answer 1

Hi jyotiahlawat,

         as given in the question an bread gives 21 KJ of energy of which  the boy can use 28% to do any work (efficiency)

         so, the work done by boy is

         21x1000x28/100 = 21x280 =5880 J

        this energy is use up by the boy to climb the tree hence

 

        mgh = 5880 J

     \therefore 40x9.8 = 5880

     \therefore h = 5880/(40x9.8) m     (i have taken g is 9.8 for easy claculation you can take according to the question)

     \therefore h = 15 meters