Thank you for reporting, we will resolve it shortly
Q.
An apple gives $21\, kJ$ energy to a boy. How much height he can climb by using this energy. If his efficiency is $28 \%$ ? (mass of boy $40\, kg$ )
BHUBHU 2007Work, Energy and Power
Solution:
Here : Energy of one apple $=2112\, J$
$=21 \times 10^{3} J$
Efficiency of the boy $=28 \%=0.28$
Mass of the boy $m=40\, kg$
Here the actual energy consumed by the boy is given by as
$=0.28 \times 21000=5880\, J$ ...(1)
and the energy consumed by the boy in climbing $h$ meter height is given by
$=m g h=40 \times 9.8 \times h J$ ...(2)
Equating equations (1) and (2) we get
$40 \times 9.8 \times h =5880\, J$
$h =\frac{5880}{40 \times 9.8}=15\, m$