text: speed or minimum flying speed, e.g., 15 per- 
  cent above the stall speed. 
  
  (2) The accclcration during the takeoff or 
  landing roll. The acceleration experienced 
  by any object varies directly with 
  the un- 
  balance of force and inversely as the mass of 
  the object. 
  
  (3) The takeoff or landing roll distance is 
  the acceleration and 
  
  a function of both 
  velocity. 
  
  In the actual case, the takeoff and landing dis- 
  tance is related to velocity and acceleration in 
  a .very complex fashion. The main source of 
  the complexity is that the forces acting on the 
  airplane during the takeoff or landing roll are 
  “difficult to define wit,h simple relationships. 
  Since the acceleration is a function of these 
  forces, the acceleration is difficult to define in 
  a simple fashion and it is a principal variable 
  affecting distance. However, some simplifica- 
  tion can be made to study the basic relatiomhip 
  of acceleration, velocity, and distance While 
  the acceleration is not necessarily constant or 
  uniform 
  the takeoff or landing 
  the assumption of uniformly acceler- 
  roll, 
  ated motion will facilitate study of the princi- 
  pal variables. affecting 
  takeoff and landing 
  distance. 