Question

The velocity of falling rain drops attains limited value because of :

• A. surface tension
• B. upthrust due to air
• C. viscous force exerted by air
• D. air current

Answer 1

Answer: (C)

viscous force exerted by air

Gravity does cause things to fall with increasing speed, but as they speed up viscous force by air increases increases. Since according to stokes law $F_r\propto v$. Eventually the acceleration stops and the raindrop reaches a constant terminal velocity.