SCIENCE SUNDAY Craziness! The Helium Balloon Car Experiment... KIDS DIDN'T SEE THAT COMING!

*********************Every Sunday is "SCIENCE SUNDAY" in our house.**********************
We love having all sorts of physics fun with accessible home experiments that explain science concepts of all complexities in awesome & exciting ways... ways that kids of all ages enjoy and (actually) comprehend.
We have such a great time doing these that we decided it might be fun to film them. Why not?!? We're doing them anyway? SCIENCE SUNDAY is an automatic in this family... whether simple, complex, or anything in between, the most important thing is that it is accessible to kids!
Check back as we upload more episodes. You may find experiments that you want to do yourself! We hope so :) Science can be a lot of fun!
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SCIENCE SUNDAY -
*********************The Helium Balloon Car Experiment****************************
We accelerate the car forward and it sends the army guy suspended from the ceiling to the back of the car, as expected. As deemed by the kids... "super obvious."
We accelerate the car forward again with a helium balloon tied to the floor (aka 'suspended' from the floor.) It sends the balloon FORWARD! Ummm... NOT as expected! As deemed by the kids....NOT super obvious.
Why does this happen? When the car accelerates, the density of the air pushes to the back of the vehicle, meaning there is literally more air in the back of the car than in the front. This is called a density gradient. As the helium balloon is in a strategically controlled stationary position in the air, it interacts with the density gradient as it is created. Since the mass of helium is lower than the mass of air, helium pushes to the front of the car as air pushes to the back!
This is described by the kids "literal craziness."