Materials:
|
- Shop Vac or any vac with a hose for suction (keep the vac under 5 horse power)
- 39 gallon or larger plastic garbage bags (I have found janitors who were able to supply
55 gallon plus bags.)
|
| Directions: |
- Have a student climb into the plastic bag and sit down so the bag is up around their
neck, but never over their head. Now place the open hose in the bag and ask the student to
hold the end. Next bring the bag together at the opening and form as good of seal as
possible.
|
| Safety Concerns: |
- The students must understand that when the vac is turned on, they must keep the end open
while keeping both the bag and their clothing from being sucked into the opening. (If the
bag does not collapse around the student, it usually means they have allowed the opening
to become covered.)
- Note: As the bag collapses around the student, it can be very revealing, so do not do
this standing up. Rather have the pressure create a ball of the student. Also remember to
turn off the vac when the student is well "Vacuum Sealed. If holes form in the bag,
simply cover them with duct tape and bag another student.
|
| Questions: |
- What do you think will happen? What do you observe? What is happening here? (Compare
class responses to bagged stuent response.)
|
| Concepts: |
- This activity demonstrates air pressure. As the bag collapses, having part of the air
inside the bag removed, the student will start to experience atmospheric pressure pushing
in on them. The ideas that the atmosphere has mass and applies pressure is very difficult
for younger students to understand. By removing a portion of this pressure, a student can
experience a little of atmospheric pressure first hand. A fun extension of upper level
classes would be to have students actually calculate the force being applied by the vac. I
have seen a teacher bring in a long metal rod that is one inch by one inch and has a total
mass of 14.7 pounds, just so they can actually experience the mass that is pushing down on
every square inch of their body (at sea level).
-
- According to Joe Stephen's Misconception book: Many students believe that blowing on
something always makes it move away. Some students believe that blowing takes the pressure
with it. For many young learners, air neither has mass nor can it occupy space. Many
children have difficulty making the connection between paper airplanes and jet airplane
flight.
-
- This activity allows students to experience air pressure first hand. Possible confusion
and misconceptions occur when: The explanations about the behavior of air and air pressure
are difficult to visualize because air is usually invisible. Many textbook presentations
begin with abstract concepts and terminology. Classroom presentations usually ignore
student's prior views and ideas.
|
