This question already has an answer here:
I had a friendly argument with my friend, and it turns out he's correct. I still don't know why I'm wrong though (haha).
Question: You are holding a bottle of soda in a car moving forward. The bubbles move upwards. Then the driver hits the breaks. Will the bubbles in the soda move forward or backwards with respect to the bottle initially?
Somehow, my answer is that the bubbles move forward with respect to the bottle, since if you just apply the breaks, the bubbles still don't feel the negative acceleration and still move upwards. Since the bottle does feel this acceleration, the bottle should accelerate in the negative direction, with the bubbles still moving upwards (and forward w.r.t the bottle).
Can someone explain why I'm wrong?