AIM OF THE EXPERIMENT: To find out how the speed of air and its pressure are related.MATERIALS: two books of the same size, a ruler, a sheet of writing paper, a drinking straw. METHOD: Lay both books on the table about 10 cm apart.
Lay the sheet of paper on the edges of both books so that it bridges them.
Point the straw under the sheet of paper between the books.
Blow through the straw as hard as you can.
RESULTS: When you blow under the sheet of paper, the sheet bends downwards.
WHY? Before you began to blow through the straw, the pressure of the air acted equally on the sheet of paper from above and from below. As the speed of the airflow under the sheet of paper increases, the air pressure on the other side of the sheet comes to exceed the pressure below, which falls. In this way the now greater air pressure on the sheet from above bends it downwards.