Experiment 1:
The Straw Drinking Race
Materials:
1. Two identical drinking straws ( one punctured with a few needle holes ober the whole length).
2. Two small cups and some soda drink.
Procedures:
1. Fill the two small cups halfway with soda pop.
2. Ask two students to come up and comment: "Who would be the better 'sucker'?", and give each of them a straw (one of them with holes in it, but do not mention this).
3. Let them start drinking (sucking) on the count of three.
4. Give another pair of students a turn to race (the one who has the straw with the holes always loses).
Explanation:
By sucking we are creating a partial vaccuum or a lower pressure in the straw above the liquid that we drink. The higher pressure in the atmospheric air pushes the liquid up the straw in our mouth.
The student with the leaky straw sucks in air and thus cannot create a vaccuum above the liquid, so the liquid is not pushed up.
If there were no air pressure in the atmosphere, we would not be able to suck liquids through a straw. If the mouth of an astonaut was connected to a straw through his space suit to an open cup with liquid on the moon surface, he would not be able to drink the liquid by sucking that will push it up the straw.
Experiment 2:
The Ballon Air Lift
Materials:
1. One medium sized balloon for each student in the class
2. Straws for each student in the class
3. Duct tape
4. a table
5. Cork board
6. Additional heavy items to add
Procedures:
1. Before class attach the balloons to the end of the straw with duct tape.
2. Ask as many students as can possibly stand around the table to stand around the table and give them each a balloon (with the attached straw)
3. Let them put the balloons on the table and hold the end of the straw in their mouth (mak sure they are in a squatting position around the table).
4. Make sure that will students are ready to blow air into the balloons with their hands and fingers away from the table.
5. Place the cork board on top of the balloons
6. Let the students blow into the balloons.
7. Repeat with other heavy objects on top of the cork board.
Explanation:
By blowing in the plastic bags, air is being compressed. This compressed air is exerting pressure underneath the inverted table causing the table to rise. This principle is being applied when pumping tires of a bicycle or automobile, or compressing air in air lifts (at gas stations or garages). Tire pressures are twice or four times as high as the atmospheric pressure, and in air lifts these pressures go as high as 20 to 30 atmospheres.