question_answer

A boy of mass 70 kg, run up a flight of 50 stairs, each measunng 0.20 m in 20 s. Calculate, (i) Force acting on the body (ii) Work done by the body (\[\text{g}=\text{1}0\text{m}{{\text{s}}^{-\text{2}}}\])

Answer:

Given, \[m=70\,\,kg\] Height of each stair \[(h)=0.20\,\,m\] \[\therefore \] Height of 50 stairs \[=50\times 0.20=10\,\,m\] \[g=10\,\,m/{{s}^{2}}t=20s\] \[F=?W=?\] (i) We also know, \[W=mgh\] \[\Rightarrow F=70\times 10=700\,\,N\] (ii) We also know, \[W=mgh\] \[\Rightarrow W=70\times 10\times 10=7000\,\,J\]