Physics quiz question: dynamic fluid viscosity

Physics 205A Quiz 1, fall semester 2013
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problems 1.37, 1.39

The kinematic viscosity ν of a fluid (measured in units of m²·s^–1) is given[*] by the expression:

ν = u/ρ.

The density of the fluid ρ is measured in units of kg·m^–3. The units for the dynamic viscosity u are:
(A) kg^–1·m·s.
(B) kg^–1·m⁵·s.
(C) kg·m^–5·s^–1.
(D) kg·m^–1·s^–1.

[*] wki.pe/Viscosity#Kinematic_viscosity.

Correct answer (highlight to unhide): (D)

Replacing the quantities in the equation with their kg, m and s units, except for the dynamic viscosity u:

m²·s^–1 = u/(kg·m^–3),

m²·s^–1 = u·kg^–1·m³,

kg·m^–1·s^–1 = u.

Sections 70854, 70855, 73320
Exam code: quiz01cH3E
(A) : 6 students
(B) : 12 students
(C) : 9 students
(D) : 49 students

Success level: 64%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.55