Physics - Fluid Question with Solution | TestHub

Total volume of rain drops, received $100\mathrm{cm}$ in a year by area $1{\mathrm{m}}^2$ $$=1{\mathrm{m}}^2\times \frac{100}{100}\mathrm{m}=1{\mathrm{m}}^3$$ As we know, density of water, $$d=10^3\mathrm{kg}/{\mathrm{m}}^3$$ Therefore, mass of this volume of water $M=d\times v=10^3\times 1=10^3\mathrm{kg}$ Average terminal velocity of rain drop $v=9\mathrm{m}/\mathrm{s}$ (given) Therefore, energy transferred by rain, $$\begin{array}{rl}& E=\frac{1}{2}m{v}^2\\ & =\frac{1}{2}\times 10^3\times (9{)}^2\\ & =\frac{1}{2}\times 10^3\times 81=4.05\times 10^4\mathrm{J}\end{array}$$