text: The momentum j-factor in the Chilton-Colburn analogy is given by a number describing this phenomenon, divided by two.
full_question: The momentum j-factor in the Chilton-Colburn analogy is given by a number describing this phenomenon, divided by two. A constant factor of 1.33, times the square root of the Reynolds number, gives the magnitude of this phenomenon on a flat plane. For high Reynolds numbers, the magnitude of this force is proportional to the velocity squared, but in creeping flow, the dependence is (*) linear, with a coefficient often symbolized b. This force is proportional to the radius and viscosity according to Stokes' Law for spherical particles. The "form" contribution to this force is greater when a surface is perpendicular to the oncoming streamlines. For 10 points, name this force that balances gravity at the terminal velocity, and opposes thrust in fluids. 
first_sentence: The momentum j-factor in the Chilton-Colburn analogy is given by a number describing this phenomenon, divided by two.
raw_answer: drag force [or air resistance; prompt on air friction 