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graduated pulley radius r
additional mass m
= 50 g
J
distances r
= 30 mm, 50 mm, 70 mm, ...210 mm
J
•
Set up the experiment as described under 6.1.
•
Determine the times for the same angle of
rotation with different distances r
additional mass and calculate the corresponding
moments of inertia J using Equations 4, 5 and 1.
•
Display the dependence of the moment of inertia
J on the distance r
J
diagram.
7.4 Time measurements using a digital counter
and the laser reflection sensor
By using the start/stop unit and the laser reflection
sensor, it is possible to make exact measurements
over defined angular segments (see Fig. 1). Operating
the lever (b) releases the brake that is holding the disc,
and simultaneously a switch contact between the two
sockets
(c)
is
opened
measurement. A laser reflection sensor can be used to
stop the time measurement at a predetermined
position without touching the disc and without a time
delay.
Warning: do not look into the laser beam!
•
Place a laser reflection sensor on the bracket of
the start/stop unit (magnetic holding mechanism).
•
Connect the start/stop unit to the counter's start
signal input and the laser reflection sensor to the
counter's stop signal input.
•
Position the laser reflection sensor so that the
light beam passes through the hole at the 0°
position. (Tip: cover the hole with a strip of paper
– the laser light is easily visible through the
paper.)
•
Turn the rotating disc to the desired position on
the scale and hold it there with the pointer by
moving the lever to its upper position. The
pointer should be only in slight contact with the
edge of the disc.
•
Press the lever down to start the rotation and the
time measurement.
The time measurement stops when the light from the
laser falls on the hole at the 0° position or on a mark
on the underside of the large rotating disc (including
in the set of additional accessories).
Elwe Didactic GmbH • Steinfelsstr. 6 • 08248 Klingenthal • Germany • www.elwedidactic.com
3B Scientific GmbH • Rudorffweg 8 • 21031 Hamburg • Germany • www.3bscientific.com
= 10 mm
M
J
of the additional mass in an r
and
starts
the
Technische Änderungen vorbehalten
© Copyright 2008 3B Scientific GmbH
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- J
J
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