Properties of Air and The Characteristics of Flight
- we know it exists,
- it’s all around us,
- we see moving trees,
- it fills our lungs,
- it has substance but can’t be seen
- we can’t taste it, but
- we can feel it.
- colourless, odourless and tasteless,
- a gas made mainly of nitrogen (78%), oxygen (21%) and small amounts of carbon dioxide, hydrogen and
What do we know about air? What have we observed?
Air is matter so it must be made up of molecules and atoms. It interacts with objects because we can see the trees swaying in the breeze. We also know it moves things since we can see the clouds moving in the sky and storms approaching us in the distance. We know that the air must move because it brings us our weather. Air can change temperature - we can feel the temperature of the air against our skin. Sometimes air can smell. It is able to carry the smell of roses to our noses or for that matter an angry skunk, too. We know that hot air rises and that hot air can hold more moisture. We see birds using the air to travel from place to place and we also see seeds being blown around by the wind. We know that the air can become quite dirty from dust but also quite polluted. Sometimes we can see the pollution or smell the pollution. We know that air must take up space because we have all blown up a balloon or put air in our bicycle tires.
Air has mass: To show this to be true, you will need a balloon and an accurate scale (a scale that is capable of measuring very small amounts such as grams). Place the empty balloon on the scale and record its mass. Next, blow up the balloon and knot the end. Place the inflated balloon on to the scale and record its mass. Compare the two masses.
Air has pressure: To show this to be true, you will need two sheets of regular notebook paper. Hold the two sheets of notebook paper about eight cm apart. Blow between them. Instead of flying apart they come together. The air moving rapidly between the two pieces of paper has less pressure than the air pressing on the outer sides of the paper.
Air has temperature: To show this to be true, take a couple of thermometers and put them in different places such as in the classroom, outside or in the refridgerator. Take the readings. To show that warm air expands and cold air condenses then try the balloon experiment. You will need hot water, a pop bottle and some ice. click here
A rise in pressure must always be accompanied by a decrease in the speed or a increase in the speed results in a decrease in the pressure.
Let's give an example to help explain this.
Try This:The next time you have a shower, as soon as you turn on the water, check out the shower curtain. The shower curtain gets pulled inwards. Why? The increased speed of the water/air inside the curtain (compared to the still air outside the curtain) causes a pressure drop. This difference between the inside and outside causes the shower curtain to be sucked inwards.
Concerning flight, Bernoulli's Principle has to do with the shape of an airplane's wing. The bottom is flat, while the top is curved. Air travels across the top and bottom in the same time, so air travels slower on the bottom (creating more pressure) and faster on top (creating less pressure). Bernoulli's Principle
Try This:Take a strip of paper (6 cm by 20 cm). Hold one end of the paper and rest it against your chin, just below your mouth. Hold it in place with your thumb and blow over the top of the strip. The paper rises. Try the same thing after you have fastened a paper clip on the end of the strip. See how many paperclips you can lift in this way. It doesn't matter whether you move the air over the strip of paper by blowing or whether you move the paper rapidly through the air - either way it rises.
For several experiments dealing with air pressure, force, velocity, wind tunnels
Bernoulli's Principle can be found at work all around you. For example: if you enjoy sports and play baseball, tennis or golf you just might be using Bernoulli's Principle. A good pitcher is able to throw a curve ball.. Why do you think the ball curves when thrown? In golf, a pro golfer is able to hit the ball so that it curves either right or left. What causes this curve? A tennis player is able to put a top spin on the ball so that the tennis ball curves down. Think of the air pressure! Here's another example. In your homes I'm sure you havespray cans or spray bottles. These work using Bernoulli's Principle, but how? Why not take one apart and try to figure out how? Did you know that many animals that burrow use Bernoulli's Principle, too. How?