PASCO SE-9409 ELASTIC CORD - Manual

Instruction Sheet
for the PASCO
Model SE-9409
ELASTIC CORD
Phone (916) 786-3800 • FAX (916) 786-8905 • TWX 910-383-2040
10101 Foothills Blvd. • P.O. Box 619011 • Roseville, CA 95678-9011 USA
better
teach physics
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Introduction
Elastic or “Bungie” cord is a
most useful item in the physics
class. Just a few of the experi-
ments and demonstrations for
which you can use it are described
below.
Additional Equipment
Recommended:
• Wave Driver, WA-9753 or
SF-9324
• Sonic Ranger, ME-9346 (Apple) or
ME-9381A (IBM)
• Mass and Hangers, ME-9348
Setup Procedure
➀
Horizontal waves, mechanically driven.
Secure both ends of a length of cord and use a mechani-
cal driver, (PASCO Model WA-9753 for example) to
drive the cord. As one varies the frequency, the cord
will produce excellent wave patterns at the various
multiples of wavelengths. Change the tension and
examine its effects on the frequencies.
➁ Horizontal waves, driven by hand.
Secure one end of the cord and set up standing waves.
You will want low frequency waves for this, so use a
long length of cord and relatively low tension. You can
produce standing waves, or just give the cord a sharp
pulse and watch the pulse travel down the cord and
reflect back.
➂
Vertical waves may be performed in the same way as
horizontal waves.
√
A very long spring.
Use the cord instead of a spring for large demonstra-
tions. Hang a mass, let it drop, and observe the period
of oscillation. Use a sonic ranging system (the PASCO
Sonic Ranger for example) to measure displacement as a
function of time. The Bungie cord will stretch about
two times its length and has the advan-
tage over springs that it is almost
impossible to over stretch.
➄ A safe Bungie cord jumper.
Bungie cord jumping has become
a popular sport. You can simulate it
in your class room by attaching a
length of the cord to the ceiling and a
mass (about 250 g is good) to the end.
Keep the length of the Bungie
cord to about 1/3 of the height
of the room. If the motion can
be kept primarily in the vertical
plane, one can monitor the results with a Sonic Ranger.
≈
Energy conversion.
Hang a mass from the cord, then pull the mass down
and release. The amplitude of each oscillation will be
less than the previous. By monitoring the decreases in
amplitude, the amount of energy lost per oscillation can
be calculated. The total energy of a particle in simple
harmonic motion is proportional to the square of the
amplitude of motion.
∆
Spring constant.
One can confirm Hooke’s law, the description of the
relationship between the force applied to a spring and its
stretched length (F
net
= -kx). Measure the unstretched
length of a piece of Bungie cord. Hang a known mass
from the end of the cord and measure the cord’s
stretched length. Determine the spring constant: “k” =
F/x (F = mg = force applied by the known mass; x = the
difference between the stretched and unstretched
length). Vary the amount of applied mass and measure
the corresponding amount of stretch. Plot applied force
versus amount of stretch.
➤ NOTE: To make the Bungie cord even
more visible, dye it with RIT fluorescent dye
or use a fluorescent “High Lite” type pen.
012-04500C
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$1.00