Blow through the spool and let go of the pin and card. Make sure the spool has only one main hole. In the early 1700s, a Swiss mathematician named Daniel Bernoulli discovered that when flowing air or water changed its speed, its pressure also changed. Squeeze the Stream Fluids, such as air and water, change speed as they flow between and around objects. To see how this happens, build this tiny stream channel.
Tape pencils on a cookie sheet so that they make a channel that starts out wide, then narrows.
Now barely tilt the cookie sheet against the sink and slowly pour soapy water into the channel. Air is pushing on you right now from every direction. We're so used to air being around us that we often don't notice it. This constant push of air is called air pressure. If you tried blowing between them, you disturbed this push in a very special way.