Q. A rain drop of radius 0.3 mm has a terminal velocity in air $= 1\ ms^{- 1}$. The viscous force on it is
A) $101.73 \times 10^{- 4}\ dyne$
B) $101.73 \times 10^{- 5}\ dyne$
C) $16.95 \times 10^{- 4}\ dyne$
D) $16.95 \times 10^{- 5}\ dyne$
Explanation
(a) $F = 6\ \pi\ \eta\ r\ v$
$= 6 \times 3.14 \times (18 \times 10^{- 5}) \times 0.03 \times 100$
$= 101.73 \times 10^{- 4}\ dyne$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.