Monday, June 14, 2010 Air Pressure: Straw Fountain Fill a cup
part way with water. Hold a straw vertically in the water – make
sure it’s not touching the bottom of the cup. (You could
probably tape the straw to the cup if you’re having a hard time
holding on to all of the parts.) Using another piece of straw,
blow across the top of the straw that’s in the water. Water
shoots out of the vertical straw. Normally there’s a whole lot
of air molecules stacked up on top of the surface of the water.
When you blow across the top of the straw, you’re pushing some
of those air molecules out of the way. There are still air
molecules pushing on the rest of the water, and with the
pressure over the straw reduced, the water is pushed up the
straw. If you're having a hard time getting the water to shoot
out of the straw, try some of these tips - they helped me! 1 -
Aim the straw you're blowing through slightly up (see picture
above). 2 - Use shorter pieces of straw. 3 - Fill the cup with
more water. 4 - Practice - it takes