3B Scientific Variable g Pendulum User Manual

3B SCIENTIFIC

Variable-g Pendulum U8403950

Instruction Sheet

05/09 THL

®

PHYSICS

1 Pendulum bob
2 Pendulum rod
3 Disc with scale
4 Pointer
5 Pendulum clamp
6 Knurled screw (rear of disc with

scale)

1. Safety instructions

When used correctly the instrument should not
present any risks.

The instrument requires a good degree of stability
as there is a danger of it tipping over.

• Set the instrument up securely in the stand

base so that there is no risk of tipping over.

2. Description

The instrument is used to measure the period of a
pendulum as a function of the length of the
pendulum and the effective component of the
earth’s gravitational field (“acceleration due to
gravity”).

It can be used, for example, to simulate the effects
on the period of the pendulum that would be
observed on the surfaces of planets or other bodies
of lower mass than Earth, such as the moon or
Mars.

1

The effective gravitational field influencing the
periodic motion is reduced according to the
inclination of the plane of the pendulum relative
to the vertical. The axis of rotation lies along the
pointer, the inclination of which can be varied
between 0° und 90°.

The mass of the pendulum rod is small compared
to that of the pendulum bob (the discs), and
therefore the arrangement approximates closely to
an ideal mathematical pendulum, so that it is
described by the relationship:

l

T 2

⋅π⋅=

.

α⋅

cosg

The length l of the pendulum can be assumed to be
the distance between the pendulum sleeve and the
lower surface of the pendulum bob.

The bob can be moved along the pendulum rod
and secured by means of a screw.

The pointer is provided with a hole into which it is
possible to screw a mounting rod (U8403955) for a
photo gate.

3. Equipment supplied

• Set up the instrument on a level surface using

the large stand base and rod, positioning it as
low as possible so that there is no risk of
tipping over.

• Adjust the base so that the rod is exactly

vertical.

• Set the angle of inclination α, by loosening the

knurled screw (6), moving the pendulum rod
and pointer to the required angle on the scale,
and re-tightening the screw.

To measure the frequency or period of the
pendulum, a photo gate (U11365) can be attached
using the mounting rod (U8403955) as shown in
Fig. 1.

1 Pendulum rod
1 Disc with scale
1 Pointer
1 Pendulum bob

4. Technical data

Pendulum bob: 300 g
Length of pendulum rod: 350 mm
Scale markings: 0° … 90°

5. Operation

In order to carry out the experiments, the following
equipment is also required:

1 Stand base, A-shaped U8611150
1 Stainless steel rod U8611330
1 Mechanical stopwatch U40801
or
1 Photo gate U11365
1 Mounting rod for light barrier U8403955
1 Digital counter (230 V, 50/60 Hz) U8433341-230

or
1 Digital counter (115 V, 50/60 Hz) U8433341-115

Fig. 1 Variable-g pendulum with mounting rod and
photo gate

Elwe Didactic GmbH ▪ Steinfelsstr. 6 ▪ 08248 Klingenthal ▪ Germany ▪ www.elwedidactic.com

3B Scientific GmbH ▪ Rudorffweg 8 ▪ 21031 Hamburg ▪ Germany ▪ www.3bscientific.com

Subject to technical amendments

© Copyright 2009 3B Scientific GmbH