Flag in a Vacuum
Suppose you have a miniature replica of the American flag on a pole, with a thin rod supporting the top of it, and you decide to put it into a closed container. You then suck all of the air out of this container until it becomes a vacuum chamber (that is, the container now has little to no air resistance or drag). What happens to the flag when you shake the vacuum?
Bonus 1: What will happen when you stop shaking the vacuum?
Bonus 2: What will happen when you put air into the vacuum?
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1 solution
It is sometimes assumed that if an object like a flag is placed in a vacuum, say like outer space, then the flag cannot “flutter” because of the lack of wind.
However, what does exist both on Earth and in space is an object’s tendency or resistance to move when a force is acted on it, this is known as its inertia. Although the air resistance in the vacuum is significantly different than that outside of it, the flag will still nonetheless move as if it were not in a vacuum, just as long as you have something acting on it.
For this same reason, even when you stop applying forces onto the flag, the flag will simply go back to flopping over. Hence why there would be a support rod to keep the flag up straight.
Finally, if you reintroduce all of air into the vacuum all at once, the air would rip the flag apart, as the pressure on it has changed dramatically.
Here’s a video where you can learn more on this subject: https://m.youtube.com/watch?v=_F0ZZ8Nus1Y