Two men A and B each of mass $50 \mathrm{kg}$ and $80 \mathrm{kg}$ climb through a height $10 \mathrm{m}$. A takes $30 \mathrm{s}$ and B takes $50 \mathrm{s}$ to reach. Find the difference in powers expended by each? What is the importance of managing ideal body weight? What values one need to inculcate for it?

A water pump lifts water from a level $10 \mathrm{m}$ below the ground. The water is pumped at the rate of$30 \mathrm{kg}/\min$ with negligible velocity. Calculate the minimum power the pump should have to do this work.

Pratyush can run at a speed of $8 \raisebox{1ex}{$\mathrm{m}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{s}$}\right.$ against the frictional force of $10 \mathrm{N}$. His friend Adarsh can move at a speed of $3 \raisebox{1ex}{$\mathrm{m}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{s}$}\right.$ against the frictional force of $25 \mathrm{N}$. Who is more powerful and why?