Question

A bread gives a boy of mass $40kg$ an energy of $21kJ$. If the efficiency is $28$% then the height can be climbed by him using this energy is

• A. $22.5m$
  
• B. $14.7m$
  
• C. $5m$
  
• D. $10m$
  

Answer 1

The correct option is B $14.7m$

$\eta =28\%$

$E_{e}ff=E\ast \eta =21\ast {10}^3\ast 0.28=5880J$

$E=mgh⟹h=\frac{E}{mg}=\frac{5880}{40\ast 10}=14.7m$