Observing the lack of this phenomenon in an incompressible and inviscid flow was key to the resolution of D'Alembert's paradox.
A term for the inertial force and a term for this phenomenon are added on the right-hand side of the Morison equation. In that equation, this phenomenon is calculated as one-half times the mass density, the velocity squared, the reference area, and a certain coefficient. When that coefficient describing this phenomenon rapidly decreases in response to an increasing Reynolds number, it is called the (*) "crisis" of this phenomenon. Observing the lack of this phenomenon in an incompressible and inviscid flow was key to the resolution of D'Alembert's paradox. According to Stokes' law, this force is proportional to the fluid velocity for spherical objects, and when gravity is equal to this force, an object in free fall reaches its terminal velocity. For 10 points, name this force that opposes the motion of an object in a fluid. 
A term for the inertial force and a term for this phenomenon are added on the right-hand side of the Morison equation.
drag force [or air resistance; prompt on "friction"]