Does the balloon go forward, backward, or neither?
The balloon goes forward. The reason it floats is because the air
in the car pushes it upward. When the car accelerates forward (left picture),
the air is pushed back, and the balloon is pushed forward by the air.
Its exactly as if the car were not accelerating forward but instead
were parked on a slope (right picture). The child would be pressed back into the
seat, and the balloon floats upward, namely toward the
front of the car.
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