We know two things:

1. CO2 is heavier, thus more CO2 is in the basement

2. flame is lighter, thus flame points to forward.

So can you derive that

3. more CO2 at the rear?

4. What about Oxygen?

Edited May 4, 201411 yr by cache

I think he is explaining it quite well. When you accelerate, this is actually equivalent to adding a gravitational component in the other direction (as seen from the car). The definition of "down" in the car system would therefore still be down but slightly back.

 

Now, two things to note:

1. When the car is moving at constant velocity, i.e., not accelerating, then the flame will point in the "normal" up direction.
2. When the car is breaking, the flame points to the back - the acceleration is directed in the other way.