CAP Contest question inertia I am studying for the CAP physics contest and came across this question:     "You are holding a bottle of pop in your hands on a bus. The bubbles in the pop are going straight up. Suddenly, the bus brakes hard to avoid a road hazard. How is the motion of the bubbles in the pop affected?"   I believed that since the bubbles are moving forward in their intertidal frame of reference, that they would move backwards in the drink. However, the answer is they would move towards the front of the bus. I was hoping someone would be able to help me understand why?
Why does a helium filled balloon move forward in a car when the car is accelerating? I noticed that when I had a helium filled, latex balloon inside of my car, it moved forward in the cabin as I accelerated forward. The faster I accelerated forward, the faster the balloon went from the back of the car to the front of the car. The balloon didn't have a string.  This became a game with my 4 year old as we drove home. We figured out where the balloon would go based on how fast I accelerated, turned corners etc.  I expected that it would act a lot like the water in a cup does, but it was the total opposite it seemed.  What forces caused this behavior?  I assumed it has something to do with the fluid dynamics in the closed cabin, but I can't figure it out.
Reversing Drop Bars If I need to sit more upright on an old Fuji road bike, can I turn the drop handlebars upright and reversed so that they come up and then point to the rear?  I haven't seen anything on the net from anyone who has done that.