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th
Ground.
GRA
VIT
ATIONAL
TO
RS
IO
N
BA
LA
NC
E
AP-8215
Equipment Parameters
• Small lead balls
Mass: 38.3 g + 0.2 g (
m
2
)
Radius: 9.53 mm
Distance from ball center to torsion axis:
d =
50 .0 mm
• Large lead balls
Mass: 1500 g + 10 g (
m
1
)
Radius: 31.9 mm
• Distance from the center of mass of the large ball to the
center of mass of the small ball when the large ball is
against the aluminum plate and the small ball is in the
center position within the case:
b
= 46.5 mm (Tolerances
will vary depending on the accuracy of the horizontal
alignment of the pendulum.)
• Distance from the surface of the mirror to the outer surface
of the glass window: 11.4 mm
• Torsion Ribbon Material: Beryllium Copper
Length: approx. 260 mm
Cross-section: .017 x .150 mm
E
qu
i
p
m
e
n
t
S
e
t
up
Initial Setup
1.
Place the support base on a flat, stable table that is located
such that the Gravitational Torsion Balance will be at least
5 meters away from a wall or screen.
Note:
For best results, use a very sturdy table, such as an optics
table.
2.
Carefully remove the Gravitational Torsion Balance from
the box, and secure it in the base.
3.
Remove the front plate by removing the thumbscrews
(Figure 3), and carefully remove the packing foam from the
pendulum chamber.
Note:
Save the packing foam, and reinstall it each time the
Gravitational Torsion Balance is transported.
4.
Fasten the clear plastic plate to the case with the
thumbscrews.
IMPORTANT NOTES
➤
The Gravitational Torsion Balance
is a delicate instrument. We
recommend that you set it up in a
relatively secure area where it is safe
from accidents and from those who
don’t fully appreciate delicate
instruments.
➤
The first time you set up the
torsion balance, do so in a place
where you can leave it for at least one
day before attempting measurements,
allowing time for the slight elongation
of the torsion band that will occur
initially.
Keep the pendulum bob secured in
the locking mechanisms at all times,
except while setting up and
conducting experiments.
Do not touch the mirror on the pendulum.
Figure 3
Removing a plate from the chamber box
pendulum
chamber
aluminum plate
pendulum
bob
Summary of Contents for AP-8215
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