Practice question

Viscous force: F = ηvAl. η = 1.0×10−3Pa s, v = 0.7m/s, A = 0.05m2, l = 0.8×10−3m. F = 1.0×10−3×0.7×0.050.8×10−3 = 1.0×10−3×43.75 = 0.04375N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 0.044 N. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.