By Brad JenningsNovember 8, 2013
PICATINNY ARSENAL, N.J. (Nov. 8, 2013) -- Most of us are more than accustomed to pressure, both in the scientific and human sense of the word. Many, however, do not equate the significance of pressure with everyday observations.
We all know about pressure's relationship to weather patterns, bottle rockets, and air travel. Examples of pressure are not limited to these gaseous examples however. As you may remember from school, pressure is obtained by dividing a force by an applied area.
Example: The pressure you exert on the floor doubles as you switch from standing on two feet to one. It is much safer to peel an apple with a sharp knife rather than a dull knife because the sharp knife has a relatively smaller cutting surface area, thus increases the pressure applied to the apple per unit force. Being able to cut the apple with less force means a lower probability that one will slip with the knife.
Pressure is all around us. We use pressure to move and interact with the world. Pressure is measuring the force over a given area.
Pressure is a very important concept to teach to our youth because they use and interact with it every day!
1. Pressure in Relation to Airflow
Here is a simple experiment that highlights how airflow affects pressure. As air flows over an open space, it produces a low pressure zone over that region. One way to show this is to take a straw and make a slit in it such that it can be bent into an "L" shape. Stick the shorter end of this straw in a cup of water with the slit connecting the two parts of the straw about 1/4" above the water line. Then, blow through the longer end of the straw. This forces a stream of air that travels parallel to the plane that the open slit of the straw lies in.
You will notice that as you blow into the straw, liquid is brought up through the short end of the straw and is released into the atmosphere, which produces a fine mist. This highlights the pressure differential that you are creating by forcing air over the open slit at a rapid speed. This is how most atomizers and spray bottles work. This experiment can be placed into the context of why it is so dangerous if an airplane window were to crack during a flight.
How to Show Kids What Pressure Is
One easy way to teach kids about pressure differentials is the following: take a small-mouthed bottle (such as a jug or large soda bottle) and stick a small crumpled piece of paper near the mouth of the bottle (on the section of the bottle with the smallest diameter). Intuition tells us that it should be easy to blow the piece of paper into the chamber of the bottle.
However, as we blow into the bottle, the paper will come towards us rather than go into the bottle. This is because as we blow air into the bottle, we force air to the bottom of the bottle. This increases the overall pressure inside the bottle. Since the pressure inside the bottle is now greater than the pressure outside, air will rush out of the bottle, taking the crumpled up paper with it.
This issue of STEM Starters is brought to you by: The Collaboration Innovation Lab.
Serving you so you can better serve our warfighter. Please stop by the Lab for more STEM related materials you can borrow to teach your kids!
STEM Starters is produced by the DOTC STEM office to promote Science, Technology, Engineering & Math (STEM) in our youth. If you have any comments, want to write a STEM starter or have questions please contact: info @stemresource.org.
This issue of STEM starters was written and illustrated by Brandon Jennings and Ralph Tillinghast.