PASCO ME-6855 Tension Protractor - Manual (Page 4)

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T e n s i o n P r o t r a c t o r S e t - u p
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inner red scale as indicated by the red pointer. The force scale measures from 0.0 N to
10.0 N in 0.1 increments. The force measurement is accurate to ±4% of the reading.
The string can be pulled at any angle in the plane of the protractor. The string angle is read
where the string crosses the outer degree scale. The angle scale is marked from 0° to 90°
in each of four quadrants. Horizontal (to the left or right) is 0° and vertical (straight up or
straight down) is 90°. Note that the angle markings are slightly offset in order to align with
the string, which does not originate from the center of the circle but rather from a point
tangent to the pulley.
Set-up
Mounting the Tension Protractor on a Rod
Mount the Tension Protractor on a horizontal or a vertical rod using the attached
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 pointer indicates 0 N when no force is applied.
1. Allow the string to hang freely with no force applied.
2. Loosen the thumb screw on the back of the Tension Protractor (Figure 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 vertically.
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 angle 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 arrangement of string,
masses and other objects to apply tension. See the experiments on the following 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 scale where the string crosses it.
Clamp the protractor to a
vertical or horizontal rod
To zero the
force scale,
loosen and
move the
thumbscrew
Figure 2: Back view
Figure 3: Zero the
angle scale