According to the Hagen-Poiseuille law, which of the following factors influence laminar flow of a gas flowing through a conducting tube? I. density of the gas II. viscosity of the gas III. pressure gradient IV. length of the tube

A. I, III only
B. II, IV only
C. I, III, IV only
D. II, III, IV only

?ANS: D
A. Incorrect response: See explanation D.
B. Incorrect response: See explanation D.
C. Incorrect response: See explanation D.
D. Correct response: According to the Hagen-Poiseuille law of laminar flow, laminar flow is affected by (1) the radius of the conducting tube, (2) the pressure gradient, (3) the viscosity of the gas, and (4) the length of the conducting tube.