1 AFib reduces the ability of the atria to pump blood into the ventricles, and usually causes the heart to beat too rapidly. 2  One-half million new cases of atrial fibrillation are diagnosed every year in the U.S., and billions of dollars are spent annually on its diagnosis and treatment.
noun, (used with a singular verb) 1. the branch of mechanics that deals with the motion of air and other gases and with the effects of such motion on bodies in the medium. Compare aerostatics (def 1). Origin of aerodynamics.
1 The resistive force between solid surfaces in contact that resists their relative tangential motion.  2 Friction is often synonymous with dry friction. 3  The resistive force between surfaces in relative motion through a fluid (liquids & gases).  Air resistance or aerodynamic drag is a type of viscous friction.