Lately, a very interesting experiment has been done. A helium balloon was tethered to the floor of a minivan. While the minivan started moving, the balloon’s behavior seemed something different. See the video for yourself – I bet, you won’t regret it.
What’s remarkable about this experiment is that when the minivan was changing its direction, turn, speed, at the same time, the balloon’s behavior was also changing, but it didn’t change the way it should have been changed. What’s beautiful about it is that this behavior isn’t counterintuitive at all. First see the video below.
We know that the density of helium is less than air. So, when the car accelerates, the air molecules in the car resist the change in motion because of inertia and collect in the back of the vehicle’s interior. The air displaces the helium-filled balloon and causes it to move forward, away from the rear of the car where the air molecules have collected. That means, the minivan or any vehicle is actually subject to not only the usual force of gravity, but also a force pointing backwards, equal and opposite to the acceleration. Since the balloons always float “up” in a gravitational field, the balloon will point opposite to this direction, and thus it will tilt forward in the car!