• # question_answer A small sphere of radius 'r' falls from rest in a viscous liquid. As a result, heat is produced due to viscous force. The rate of production of heat when the sphere attains its terminal velocity, is proportional to                               [NEET - 2018] A)  ${{\text{r}}^{\text{5}}}$                   B)       ${{\text{r}}^{\text{2}}}$ C)  ${{\text{r}}^{\text{3}}}$                   D)       ${{\text{r}}^{\text{4}}}$

 [a] Power $\text{=6}\pi \eta r{{V}_{T}}\cdot {{V}_{T}}=6\pi \eta rV_{T}^{2}$ ${{V}_{T}}\propto {{r}^{2}}$ $\Rightarrow \,\,\text{Power }\propto {{\text{r}}^{5}}$