Hobbies And Interests
The Weight of the Air
The weight of the air, or atmospheric pressure, on an area of one square foot is a ton (2,000 lbs.). People don't get flattened into a pancake, because the same amount of air pressure inside the body is pushing in the opposite direction. To experiment with the weight of air, you need an inexpensive wooden yardstick and an entire sheet of newspaper.
Place the yardstick on the edge of a table with one half on the table, and the other half protruding over the floor. Cover the portion of the yardstick on the table with the unfolded sheet of newspaper. Hit the yardstick hard, with your hand. The yardstick breaks because the atmospheric pressure is pushing down on the newspaper, holding the yardstick down.
Under Pressure
Here's another experiment about the weight, or pressure, of air to show that the pressure inside the body pushes out equal to the atmospheric pressure pushing in. You need a clean, plastic gallon milk jug, with a screw-on lid.
Pour very hot water into the jug until it is about one-fourth full. Tightly screw on the lid. Allow the water inside the jug to cool for several hours. When the water inside the jug was hot, it heated the air molecules inside, causing them to move faster, and take up more space. As the water cooled, the air molecules slowed down, and took up less space. The higher air pressure on the outside of the jug made the jug partially collapse.
Measuring Air Pressure
Barometers are devices used to measure changes in atmospheric, or barometric, pressure. Changes in atmospheric pressure indicate future changes in the weather. You can create your own barometer with a glass soft-drink bottle; a drinking glass (sized so the soft-drink bottle can be inverted and placed in the glass without the opening of the bottle's neck touching the bottom of the glass, and so the bottle fits snugly in the opening of the glass); food coloring; and a piece of colored tape. Pick a day for this experiment when the weather is dry.
Fill the glass with room temperature water. Add several drops of food coloring until the color is dark enough to easily see through the glass. Invert the soft-drink bottle in the opening of the glass. The water should rise into the neck of the soft-drink bottle. Mark the water level with the colored tape. Observe the barometer in 24 hours. Notice whether the water level has risen, fallen or remained the same. Water will rise in the soft-drink bottle with an increase in air pressure, because the pressure is pushing harder on the surface of the water, forcing water to rise in the neck of the bottle. This indicates clear weather coming. As atmospheric pressure falls, the water level in the neck of the soft-drink bottle will fall. Precipitation is on the way.
Being Pressured
For this experiment, you need a raw potato and plastic drinking straws.
Lay the potato on a table. Without covering the hole at the top of the straw, hold the straw, and try to push it into the potato. The straw will go into the potato only a small bit. Cover the hole at the top of the straw with your finger. Try to push it into the potato in a different spot. The straw goes deeper into the potato. As the straw with the covered end pushed into the potato, the potato became a plug in the opposite end of the straw. This makes the straw stronger by increasing the air pressure inside the straw.