Practice question

Given: A sphere of radius 0.025 m moves at 0.08 m/s through blood ( eta = 2.7 × 10⁻³ Pa s ). What is the viscous drag force? These values define the system as per NCERT data. Formula: Stokes’ law: F = 6 π eta a v. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: eta = 2.7 × 10⁻³ Pa s, a = 0.025 m, v = 0.08 m/s . F = 6 × 3.14 × 2.7 × 10⁻³ × 0.025 × 0.08 = 1.017 × 10⁻⁴ N . Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.