Final answer:
The primary reference for attitude when looking inside the airplane is the airplane itself, serving as the frame of reference for determining motion and direction of objects within the aircraft.
Step-by-step explanation:
The primary reference for attitude when looking inside the airplane is the airplane itself. The airplane serves as the frame of reference for the passenger, allowing them to determine their own motion and the direction of other objects within the aircraft. Just like how passengers in a car use the car as their frame of reference to determine motion, the passenger in an airplane uses the airplane as their frame of reference.
For example, if a passenger sees a flight attendant walking toward the back of the plane, they can determine the direction of motion based on their own frame of reference, which is the stationary airplane. Similarly, if the passenger sees objects inside the airplane falling or moving, they can determine their motion and direction based on their reference frame, which is the airplane.
In summary, the primary reference for attitude when looking inside the airplane is the airplane itself, as it serves as the frame of reference for determining motion and direction of objects within the aircraft.