3B Scientific Air Cushion Plate - Manual (Page 21)

21
Physical Experiments on the Air-Cushion Table
Note:
The experiments can be repeated using different
initial positions of the piston and different mean
velocities of the hover discs. The more closely
the discs are arranged at the beginning and the
higher their mean velocity is, the quicker they
will fill out the entire area.
2.1.11 Adiabatic Compression and Expansion
of Gases
Components:
Air-cushion table with fan
Overhead projector
Magnetic barrier, long
2 Pieces
Magnetic barrier, short 2 Pieces
Magnetic piston 1 Pieces
Guide piece for magnetic piston l Piece
Hover disc, red 10 Pieces
Model simulation
Real Object Model
Vessel containing Experiment surface of
the gas the air-cushion table
surrounded by the
magnetic barriers and
the magnetic piston
Walls of the vessel Magnetic barriers
Piston to change the Magnetic piston
volume of the gas
Gas molecules
Hover disc
How to proceed:
Align the air-cushion table horizontally and at-
tach the magnetic barriers. Place the piston at the
edge of the experiment surface. To guide the pis-
ton rod, place the guide piece for the magnetic
piston onto barrier no. 2. Spread the 10 hover
discs across the experiment surface so that the
spaces between them are approximately 2.5 cm.
Then increase the fan setting so that all hover
discs are floating properly.
Rapidly move the piston to the opposite side so
that the area available for the hover discs is re-
duced to approximately one fifth. Observe the
motion of the hover discs with regard to velocity
and impacts.
Then increase the area in the same way by mov-
ing the piston back. Observe the motion of the
hover discs again.
Result:
When reducing the size of the area both the mean
velocity of the hover discs and the number of
impacts among each other and with the barriers
increase. When increasing the area, their mean
velocity decreases and the number of impacts is
reduced.
Interpretation:
Quick compression of a gas increases the mean