3
3. Description
The reversible pendulum is a physical pendulum
with two bearing fulcra plus one fixed and one
movable pendulum bob. It oscillates in its stand
either with a period of oscillation
T
1
about the first
bearing fulcrum or period
T
2
about the second ful-
crum. By shifting the movable pendulum bob it is
possible to adjust both these periods until they
are equal. The pendulum then has a reduced
length equal to the distance
d
between the bear-
ing axes and the following equation applies:
1
2
2
d
T
T
g
,
g
: acceleration due to gravity
When it is moved, the movable weight latches
into place every 2.5 cm. For finer movements the
bob can be turned by 180° about the vertical and
mounted that way round.
4. Technical data
Period of calibrated
pendulum (calculated
assuming
g
= 9.81 m/s
2
):
1794 ms
Overall dimensions:
80x125x30cm
3
Overall weight:
6.3 kg approx.
Length of pendulum rod:
120 cm
Separation between
bearing fulcra:
80 cm
Fixed pendulum bob:
1.4 kg approx.
Movable pendulum bob:
1.0 kg approx.
Pendulum deflection
max. 10 cm
5. Set-up
5.1 Choice of set-up location
If the floor on which the equipment is set is
springy, then the oscillation energy is transferred
to the whole stand and measurement errors can
then arise.
Only set up and use the reversible pendulum
on solid, level ground.
On smooth, slippery or sensitive surfaces:
Put a mat under the base plate and the strut
of the stand.
5.2 Assembly of stand
Undo the screw (see Fig. 1), fold out the
stand rod.
Secure it in its operating position with a mod-
erate degree of torque.
Fig. 1: Attachment of stand rod to stand board
5.3 Vertical positioning of the pendulum rod
Grip the pendulum with both hands and care-
fully suspend it from the bearing plate (see
Fig. 2).
The vertical positioning of the pendulum rod
should be adjusted using the positioning
screws in such a way that the bubble of the
spirit level is centered (see Fig. 3).
Fig. 2: Bearing plate with pendulum rod suspended
Fig. 3: Setting position with the help of the spirit level
