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Awesome WINDBAG Science Experiment

Tie a knot in one end of the Windbag, leaving the other end open.
Ask a friend how many breaths would it take to fill the bag?
Hold the bag horizontal and start.
You can fill the bag by holding the mouth of the bag at arm’s length. and blowing once directly into the bag. The entire bag will inflate in one breath.


The Windbag is a long, narrow plastic bag that is about 8 foot long and about 8 inches wide. The bag can be blown up the old fashion way like Grace tried in the video, which as you saw took a lot of attempts and still not close to filling part of the bag. But with the help of Bernoulli’s Principle makes it so much easier. By holding the mouth of the bag at arm’s length and blowing into the bag, you set up a region of reduced pressure, since this air is moving. Moving air always exerts less pressure than still air.


Since the outside air pressure is greater then the air pressure at the mouth of the bag, air rushes in from the room to fill the bag much faster then if you tried to blow it up the old fashion way. It might take time to get it down pat and even if you don’t get it in one breath like me, it will only take two.


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