Q. 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
A) $r^5$
B) $r^2$
C) $r^3$
D) $r^4$
Explanation
[Solution] Power = $6\pi\eta r v_t \cdot v_t$ with $v_t \propto r^2$, so P $\propto r \cdot r^4 = r^5$. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.