A syringe is used for the injection of an antibiotic solution into the muscle of a patient. For rough purposes, assume that the pressure in the muscle is 130 kPa and that the physical properties of the solution are the same as those for water. Neglecting the friction of the plunger but not the viscosity of the liquid, and assuming that the plunger moves with a speed of 1 mm/s, determine the force, F, on the plunger. Is the flow in the needle laminar or turbulent? Clearly state all assumptions that you make.

Contributed by Stavros Tavoularis, Department of Mechanical Engineering, University of Ottawa, Ottawa, Canada.