PASCO ME-6855 User Manual
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Tension Protractor
ME-6855
Instruction M anua l and
Experiment Guide
012-10381A
Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
About the Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Set-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Measuring Force and Angle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
String Replacement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
About the Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Expe r i ment 1: St atic Equ i librium with Un e qual A n g le s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Experiment 2: Boom in Static Equilibrium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Additional Experiment Suggestion: Hanging a Level Sign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Technical Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
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Tension Protractor
The string is secured
with a screw
The string is wrapped
around th e ce nt er pu lley
ME-6855
To zero the angle scal e,
rotate the outer ring
Force is indicated on the
inner scale, which is red to
match th e red po inter
Angle is indicated on the
outer scale
A mass can be hung from
the wire hook
Figure 1: Front view
Included Part s
• Tension Protractor
• String, 15 cm
• Wire hook
Other Parts Recommended
• 90 cm Steel Rod (PASCO part ME-8738)
• Large Table Clamp (ME-9472)
• Additional string (SE-8050)
• Hooked Mass Set (SE-8759)
Introduction
The Tension Protractor is used to measure s tring tension and angle si mu ltaneously. It eliminates the need for separate
spring scales and protractors in equilibrium experiments.
About the Apparatus
The Tension Protractor consists of a torsion spring scale and a protractor.
The string is attac hed to the rotating part of the protractor and wrapp ed twice around a small pulley (see Figure 1).
When the string is pulled, the torsion spring stretches and the red point er rotates. The string tension is read on the
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1
Tension Protrac tor Set-up
inner red scale as indicated by the red pointer. The force scale measures from 0.0 N to
10.0 N in 0.1 increm en ts. The force measu r ement is accurate to ±4% of the reading.
The string can be pull ed at any angle in the plane of the prot ractor. The strin g angle i s read
where the strin g cr o sses the outer degree scale. The ang le scal e is marked from 0° to 90°
in each of four quadrants. Horizontal (to the left or right) is 0° and vertical (stra ight up or
straight do wn) is 90 °. Note tha t the a ngle marki ngs a re sli ght ly offs et i n orde r to ali gn with
the string, which doe s not originate from the center of the circle but rather from a point
tange n t to th e p ulley.
Set-up
Mounting the Tension Protracto r on a Rod
Mount the Tension Protractor on a horizonta l or a vertical rod using the att ac hed
rod clamp as shown in Figure 2.
Zeroing the Force Scale:
After attaching the Tension Protractor to a rod, follow these steps to ensure that
the red pointe r ind i ca tes 0 N when n o f o rc e is applie d .
1. Allow the string to hang freely with no force applied.
2. Loosen the thumb scr ew on the back of the Tension Protractor (Fi gure 2).
3. Move the screw up or down to set the red pointer to zero on the face of the
Tension Protractor.
4. Tighten the thumb screw.
Zeroing the Angle Scale
After attaching the Tension Protractor to a rod, follow these steps to ensure that the string
crosses 90° when it is hanging vertica lly.
Clamp the protractor to a
vertical or hor i zon tal rod
To zero the
force scale,
loosen and
move the
thumbscrew
Figure 2: Back view
1. Hang a small mass on the string to act as a plumb bob (Figure 3).
2. Turn the outer ring or the protractor to rotate the angl e scale (it is held in place by fric-
tion). Align the 90° mark with the string.
Measuring Force and Angle
1. Ensure that the string is wrapped around the pulley twice so that the string is always
tangent to the pulley regardless of the string angle or tension.
2. Hang a mass from the wire hook (as in Figure 1), or set up an arra ngem ent of string,
masses and o ther obj ects to ap ply tensi on. See th e expe riments on t he foll owin g pages
for examples.
3. Read the magnitude of force on the inner red scale as indicated by the red pointer.
4. Read the angle on the outer s cale where the string crosses it.
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Figure 3: Zero the
angle sc ale
2
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