Step-by-step explanation:
In an aircraft flying straight and level, if the density doubles, the aerodynamic drag will increase by a factor of four.
Aerodynamic drag is influenced by several factors, including air density. When the density of the air through which an aircraft is flying increases, the aerodynamic drag experienced by the aircraft also increases.
According to the drag equation, the aerodynamic drag (D) is directly proportional to the air density (ρ), the square of the airspeed (V), the reference area (A), and the drag coefficient (Cd):
D = 0.5 * ρ * V^2 * A * Cd
Since the air density (ρ) is in the equation, when the density doubles, the aerodynamic drag will increase proportionally. Doubling the density means that the air density value in the equation will be multiplied by 2. As a result, the overall aerodynamic drag will increase by a factor of four (2^2).
Therefore, option (a) "increase by a factor of four" is the correct answer.