# On Saturday I was taking balloons to my neice for her birthday party

Cod
On Saturday I was taking balloons to my neice for her birthday party when I noticed something that I'd never noticed before. When I took a turn, the balloons were moving towards the center of the turn. Whenever taking a turn while driving, I realize that most objects move away from the center of the turn. So this brings a question to my mind: Why is it that the balloons went towards the center of the turn instead of away from the center? And are balloons the only objects that will do this?

## Answers and Replies

He balloons are lighter than air. What you actually see is the effect of the air inside the vehicle sloshing over to the outside of the turn, displacing the balloons toward the inside. A similar effect can be seen with a bubble level. Take one and on a smooth surface accelerate it forward. You will see the bubble go forward as if it has negative mass. Which in a sense it does.

Pandemonium
Alternatively, you may want to consider applying the principle of equivalence. When we make a turn, the centrifugal acceleration we experience is directed away from the centre of the turn. Now, using the principle, we can also think it as if we are not moving/turning at all, but there's a gravitational acceleration in the direction away from the centre of the turn.

Now, why does a helium balloon float? It is due to the lower density of helium compared to air, pushing it from the ground. So in that case above, the balloon will 'float' towards the centre of the turn. This is also another way how you can see the problem.

Andre
Good explanations, I think.

But now this. I have a bucket with water and I swirl the water around, So it's also making that same turn. Now, I drop in some sand grains, heavier than water So in analogy to the balloons, you'd expect the sand to swirl towards the outside of the turn, but instead the sand at the bottom also moves to the centre of the turn.

Now, any theory about that?

theriddler876
water is diffrent, it would be like a whirlpool type of thing, I know there's a diffrent name for it, well anything that's heavy will go to the center and sink, like if the grain of sand was a ship.

Originally posted by Andre
Good explanations, I think.

But now this. I have a bucket with water and I swirl the water around, So it's also making that same turn. Now, I drop in some sand grains, heavier than water So in analogy to the balloons, you'd expect the sand to swirl towards the outside of the turn, but instead the sand at the bottom also moves to the centre of the turn.

Now, any theory about that?

This is the same principle, the lighter air would go torwards the ouside and the heavier sand torwards the inside.

Andre
Not really, the lighter balloons are forced to the centre of the turn because buoyancy also works for centrifugal forces. Now the heavier sand that also moves to the centre of the turn cannot be explained by buoyancy. With that effect you would expect the sand moving to the outside of the turn. But it isn't. Why?