A mosquito inside a car is not hit by the back wall when the car starts moving.Why?
The air inside the car moves with the car. As far as the mosquito is concerned, it is in still air. There will be a pressure gradient in the air to accelerate the mosquito. For a larger object like a human, the air forces will not be enough to keep from moving backwards.
When a car starts moving, it goes from a state of rest to a state of motion. As the car starts accelerating, the air inside the car also starts moving due to the inertia of the car. This means that the air inside the car gets pushed towards the back of the car.
Now, let's consider the mosquito inside the car. The mosquito, being much smaller and lighter than the air molecules, will experience less resistance to the airflow. As a result, it will also move towards the back of the car in the direction of the airflow.
Since the mosquito is also moving towards the back of the car, it doesn't hit the back wall. This is because the mosquito is essentially riding along with the airflow inside the car, just like a leaf floating on the surface of a river.
So, to summarize, the mosquito inside the car is not hit by the back wall when the car starts moving because it is carried along with the airflow inside the car due to the inertia of the air molecules.