3B SCIENTIFIC PHYSICS 1018466 User manual

3B SCIENTIFIC®PHYSICS
1
Kater’s Reversible Pendulum 1018466
Instruction manual
09/16 TL/DU
1 Pendulum
2 Stand
3 Floor cover
1. Safety instructions
When carefully assembled and properly used,
safety of experimenting with the reversible pen-
dulum can be guaranteed. There is, however, a
possible risk of injury or damage to the pendulum
if care is not taken.
Read this instruction manual all the way
through and observe it in full.
Set up the stand on solid, level ground and
fasten the assembly screws tightly.
Fasten the securing screw for the movable
pendulum bob tightly so that the bob cannot
move unchecked.
Use the adjustment screws in the base plate
of the stand to align the bearing plate in such
a way that the bearing axes of the pendulum
bob can be even.
Always handle the pendulum with both hands
when setting it up or adjusting it.
Carefully suspend the pendulum from the
bearing plate and check that the bearing axes
are in the correct positions.
Do not subject the pendulum to excessive
pushes and do not deflect it by more than 10
cm at the bottom end.

2
2. Components
Pendulum
a Fixed pendulum bob
b Pendulum rod
c Bearing fulcrum
d Latch-in positions
e Movable pendulum
bob
f Securing screw
g Assembly screws
Stand
h Stand board
i Positioning screws
j Stand rod
k Stand board
l Bearing plate
m Spirit level
n Floor cover

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 T1about the first
bearing fulcrum or period T2about 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 dbetween the bear-
ing axes and the following equation applies:
12
2d TT 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/s2): 1794 ms
Overall dimensions: 80x125x30cm3
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

4
6. Operation
6.1 Moving the pendulum rod
Use gentle pressure to move the pendulum in
the direction of the arrow with several pushes
at the position marked until the deflection is
about 5 cm.
Note: Larger deflections can lead to non-negligi-
ble measurement errors.
Fig. 4: Moving the pendulum rod
6.2 Reversing the pendulum position
Use both hands to lift the pendulum out of the
bearing plate and turn it around.
Carefully suspend the pendulum from the
bearing plate by its other fulcrum. Then carry
on as in step 6.1.
Fig. 5: Experiment set-up with light barrier and digital
counter
6.3 Period of oscillation depending on the posi-
tion of the movable pendulum bob
Additionally required:
1 Light barrier 1000563
1 Digital counter (@230 V) 1001033
or
1 Digital counter (@115 V) 1001032
Set up the light barrier under the pendulum
rod while it is stationary and connect the bar-
rier to the digital counter (see Fig. 5).
Suspend the pendulum rod from the bearing
plate in such a way that both the fixed bob
(red) and the movable bob (blue) are below
their corresponding fulcra.
Attach the movable bob in the wedge-shaped
groove nearest to the fixed bob, i.e. the low-
est one. This position will subsequently be re-
ferred to as measuring point 1 (even when
the pendulum rod is suspended above the
other fulcrum).
Measure the period of oscillation and make a
note of it..
Keep moving the movable bob from one
groove to the next and secure it (measuring
points 2 –13). In each case, measure the pe-
riod of oscillation and make a note of it.
Now suspend the pendulum rod from the
bearing plate in such a way that the fixed pen-
dulum bob (red) is above the relevant fulcrum
and the movable bob (blue) is below its bear-
ing.
Secure the movable pendulum bob in the
wedge-shaped groove nearest to the fixed
bob, i.e. the highest one. This position will
subsequently be referred to as measuring
point 1 (see above).
Measure the period of oscillation and make a
note of it.
Keep moving the movable bob from one
groove to the next and secure it (measuring
points 2 –13). In each case, measure the pe-
riod of oscillation and make a note of it.
Plot a graph of the periods of oscillation de-
termined in both sets of measurements as a
function of the numbers nof the measure-
ments (see Fig. 6).

3B Scientific GmbH ▪ Ludwig-Erhard-Str. 20 ▪ 20459 Hamburg ▪ Germany▪ www.3bscientific.com
Technical amendments are possible
© Copyright 2022 3B Scientific GmbH
6.4 Determination of acceleration due to
gravity
The periods of oscillation T1and. T2are identical
at the two points where the curves intersect and
at these points they are equal to the period of os-
cillation T0of the calibrated pendulum, i.e.
T0=T1=T2.
From the period duration T0measured in step 6.3
for a calibrated reversible pendulum and a dis-
tance l= 0.8 m between the two fulcra, corre-
sponding to the shortened pendulum length, it is
possible to determine the acceleration due to
earth’s gravity:
22
0
4l gT    
.
Note: To adjust the pendulum so that both peri-
ods of oscillation are exactly the same, it may be
necessary to turn the pendulum bob by 180°
about the vertical and mount it on the pendulum
rod that way round.
7. Storage, cleaning, and disposal
Keep the apparatus in a clean, dry, dust-free
place.
Do not use aggressive cleaning agents or sol-
vents to clean the apparatus.
In order to clean the equipment, use a soft,
damp cloth.
The packaging should be disposed of at local
recycling centres
If the equipment itself is
to be disposed of, it
must not be included
with normal household
waste. Local regula-
tions are to be obeyed.
Fig. 6: Period of oscillation Tas a function of measuring point number n. Red circles: Both pendulum bobs below
fulcrum. Black squares: Fixed pendulum bob above fulcrum, movable bob below