For straight and level flight, the forces must be in what state?

For straight and level flight, the forces must be in what state?

• A. Dynamic equilibrium
• B. Static equilibrium
• C. Equilibrium of forces
• D. Constant acceleration

Answer: (B)

In steady, straight-and-level flight the forces are balanced, so there is no net force and no acceleration. Lift exactly supports weight, and thrust exactly counters drag. Because the net force is zero, the aircraft maintains its current speed and direction, continuing straight at a constant altitude. This steady, force-balanced state is described here as static equilibrium, since the motion remains constant and there’s no change in velocity. (If you consider the broader physics terminology, some would call this dynamic equilibrium because the aircraft is moving, but in this context the focus is on the forces balancing to prevent acceleration.)

In steady, straight-and-level flight the forces are balanced, so there is no net force and no acceleration. Lift exactly supports weight, and thrust exactly counters drag. Because the net force is zero, the aircraft maintains its current speed and direction, continuing straight at a constant altitude. This steady, force-balanced state is described here as static equilibrium, since the motion remains constant and there’s no change in velocity. (If you consider the broader physics terminology, some would call this dynamic equilibrium because the aircraft is moving, but in this context the focus is on the forces balancing to prevent acceleration.)