Flies (and other flying insects) can keep up inside a moving car due to their remarkable flying abilities and some specific factors related to the car's motion.
Flying Adaptations: Flies have evolved with highly efficient flight mechanisms. Their wings are designed to generate lift and thrust efficiently, allowing them to stay airborne and maneuver easily.
Airflow: When the car is moving, it creates airflow inside the cabin due to the pressure difference between the outside and inside. This airflow allows flying insects like flies to get carried along with it. The air movement inside the car provides an additional force that helps them stay airborne and move with the vehicle.
Open Windows: If the car has open windows or doors, it provides an easy entry point for flies and other insects. Once inside, they will take advantage of the air currents and find a spot where they can catch the airflow and remain aloft.
Insect Behavior: Flies are agile insects with quick reflexes. They are capable of making rapid adjustments to their flight patterns, enabling them to respond to changes in the car's motion and maintain their position.
Low Air Resistance: Inside the car, there is relatively low air resistance compared to flying outside in still air. This means that flies do not have to exert as much energy to fly within the car, making it easier for them to keep up with the vehicle's movement.
Overall, the combination of their flying abilities, the airflow inside the car, and their adaptability to changing conditions allows flies to keep up and fly around inside a moving vehicle.