PASCO ME-9341 INTRODUCTORY ROTATIONAL APPARATUS - Manual (Page 9)

5
012-03051F Introductory Rotational Apparatus
11 Attach a pulley to the base of the apparatus using
the Smart Pulley table clamp as shown in Figure 3.
If you don't have the table clamp, a pulley mounted
to a ring stand can be used, as long as the height
and angle of the pulley are adjustable. 12 Pass the thread over the pulley and adjust the pulley
angle and height so the thread is parallel with the
platter surface and with the groove in the pulley.
NOTE: When using a falling mass to accelerate
the platter, there are two setup options.
Option a—This option requires the Smart Pulley
and a second pulley, set up as shown in Figure 3.
This method is slightly less accurate than option
b, but conceptually simpler. When entering the
graphing mode of the Smart Pulley software, you
will be asked to identify the type of device being
used to interrupt the photogate. If you are using
the version of Smart Pulley Timer software that
functions with either 10-spoke or 3-hole pulleys,
simply choose ROTATIONAL APPARATUS.
If you are using an older version of Smart Pulley
Timer and a 3-hole pulley, choose ROTATIONAL
APPARATUS. However, if you are using an
older version of Smart Pulley Timer software and
a 10-spoke pulley, choose OTHER (ANGULAR
MEASUREMENT). The computer will ask you
to enter the angle in radians between the spokes.
Enter 0.125 [calculated by using
θ
= 2
π
/10
(R
SMART PULLEY
/R
MAIN PLATTER
)]. The computer
will then automatically convert the measured
times to determine the angular displacement,
velocity, and acceleration of the platter. The
slight decrease in accuracy results from the
friction caused by the pressure of the Smart
Pulley on the rim of the spinning platter.
Option b—In this option, use the Smart Pulley
as the pulley that supports the hanging weight.
No other pulley is needed. When asked by the
computer to identify the type of device being
used to interrupt the photogate, select option F—
OTHER (ANGULAR MEASUREMENT). You
will then be asked to enter the angle between
openings. Enter one of the values shown below,
depending on which tier of the step pulley you
are using and the type of Smart Pulley you have
(these values are the angle, in radians, through
which the platter turns for each signal sent to the
computer by the Smart Pulley).
Tier of step pulley used 3-hole 10-spoke
Smallest 3.20 1.00
Middle 2.49 0.75
Largest 1.92 0.60
These values can be calculated using the formula:
θ =
2 /3 (R
p/
R
sp
) for a 3-hole pulley
or
θ =
2 /10 (R
p/
R
sp
) for a 10-spoke pulley
where R
p
is the radius of the Smart Pulley
groove, and R
sp
is the radius of the tier of the
step pulley that is being used.