Materials Required
  • A transparent straw
  • A glass of water
  • A blade

How to do it

  • Take the straw and make a small cut in the middle of the straw.
  • Bend the straw  to 90 degree.
  • Now, place one end of the straw in the glass of water and the other end in mouth of your kid.
  • Ask the kid to blow the air through the straw and ask her to observe what happens.
  • Few water will rise up in the vertical straw.

Explanation

  • Moving air exerts less sideways pressure than still or less turbulent air around it.
  • The moving air at the upper end of the straw(which is kept in the mouth) reduced the pressure in the vertical straw.
  • As the atmospheric pressure on the surface of water was greater than the pressure in the straw, few amount of  water was forced to rise up into the straw.