Question Detail
Question
A small metal sphere with diameter 10mm is dropped into glycerin. The viscous force on the object is 2.5N. If the terminal velocity of the object is 6 m/s calculate the coefficient of viscosity η of the fluid.
Correct Answer
Option C is the correct answer.
Detailed Explanation
At terminal velocity, viscous force F = 6πηrv. Radius r = 5 mm = 0.005 m. So, η = F / (6πrv) = 2.5 / (6π × 0.005 × 6) = 2.5 / (0.18π) ≈ 2.5 / 0.565 = 4.42 Nsm⁻².
Hint
Use Stokes' Law for viscous force: F = 6πηrv.