text: Figure 1.3 illustrates the variation of static, 
  flowing 
  dynamic, and total pressure of air 
  the total 
  through a closed tube. Note that 
  pressure is con,stant throughout 
  the length 
  and any change in dynamic pressure produces 
  the same magnitude change in static pressure. 
  The dynamic pressure of a free airstream is 
  the one ‘common denominator of all aero- 
  dynamic forces and moments. Dynamic pres- 
  sure represents the kinetic energy of the free 
  airstream and is a factor relating the capability 
  for producing changes in static pressure on a 
  surface. As defined, the dynamic, pressure 
  varies directly as the density and the square of 
  the velocity. Typical values of dynamic pres- 
  sure, 4, are shown in table l-1 for various true 
  airspeeds in the standard atmosphere. Notice 
  that the dynamic pressure at some fixed veloc- 
  ity varies directly with the density ratio at any 
  altitude. Also, appreciate the fact that at an 
  altitude of 40,oM) feet (where the density ratio, 
  b, is 0.2462) it is necessary to have a true air 
  twice that at sea level in order to 
  velocity 
  product the same dynamic pressure. 