Tuesday, November 21, 2017

100 Days of Science #9-- Wind Tunnel

We tried another fun science experiment that shows how wind can create a tunnel through two tall skyscrapers and cause them to want to pull towards one another.

We talked about how architects would need to keep this phenomenon in mind when drawing up plans for city buildings.

For this experiment we needed:

2 balloons
some water
some string
a pole
two matching chairs
empty paper towel tube (optional)

We put a bit of water in our balloons and blew them up.  Then we suspended the balloons from our pole (we used a broomstick) and made sure they were spaced just a few inches apart.


We only added enough water to keep the balloons somewhat weighted down and steady (you can see in this photo that it didn't take much water).



Once we were happy with our balloons we tried blowing air through the middle of them, sometimes using a paper towel tube. 




I honestly thought this experiment was going to be a failure. Both Evan and I could not get the balloons to move at all when we blew next to them.  Then Alec came over and gave a great big blow and we watched the balloons pull so close together they actually touched a time or two!




I had to take a moment to laugh like crazy over the faces Alec was making as he was blowing!  They were cracking us all up but I was so happy to see the experiment working!!

Here's how it works:  the wind going through the balloons is at a higher speed and when gases move at higher speeds that they loose pressure.  BUT the air on all other sides of the balloon have the same air pressure they always had and since the outside forces have greater air pressure they push inward when the air is moving quickly through the gap in the balloons and that forces the balloons together.  

It was pretty neat to learn that architects have to take this wind tunnel effect into account when designing skyscrapers because changes in air pressure can put added stress on city buildings.  


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