Practice question
Question
A sphere of radius 0.03m falls through machine oil (η\=0.113Pa s) at 0.15m/s. What is the viscous drag force?
Explanation
Stokes’ law: F = 6πηav. η = 0.113Pa s, a = 0.03m, v = 0.15m/s. F = 6×3.14×0.113×0.03×0.15 = 0.0958N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 0.096 N. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.