PASCO ME-9341 INTRODUCTORY ROTATIONAL APPARATUS - Manual (Page 10)

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Introductory Rotational Apparatus 012-03051F
If you don't have the Smart Pulley system, a PASCO
photogate can be used to time the Rotational Appara-
tus. Other photogates can be used as well. The
Rotational Apparatus includes a mounting clamp that
should work with most photogates.
To Use a Photogate:
➀ Mount the photogate in the photogate clamp, and
mount the photogate clamp in the pulley clamp, as
shown in Figure 5.
➁ Tape a piece of cardboard to the top of the platter
to trigger the photogate. The shape of the card-
board depends on which of the following timing
techniques you choose.
PASCO photogates have three timing modes: Pulse,
Gate, and Pendulum. If your photogate has these
timing modes, any of the following four timing
techniques can be used:
1. PULSE MODE (Method 1)—In pulse mode, the
photogate will be triggered each time the leading
edge of the cardboard interrupts the photogate
beam (see Figure 5). The times displayed will
therefore show the time for one full revolution of
the platter. Experimenters will then have one
revolution to record the time before a new time is
displayed. (Just divide 2 by the measured time to
determine the angular velocity of the platter in ra-
dians/second.)
2. PULSE MODE (Method 2)—Tape two pieces of
cardboard to the main platter (see Figure 6). If the
cardboard pieces are accurately placed so the lead-
ing edges are along a single diameter of the platter,
the timing resolution is twice as good as with a
single cardboard piece. The displayed times will
show the time per 1/2 revolution of the platter.
3. GATE MODE—Tape a one radian sector of card-
board to the top of the main platter (see Figure 7).
In gate mode, for each revolution of the platter, the
timer will display the time during which the card-
board interrupted the photogate. The reciprocal of
the measured times will therefore give the angular
velocity in radians/second. (See the Appendix for
a one radian sector that you can copy and use as a
template for cutting the cardboard.)
One Radian
Sector
Photogate
Cardboard
Pulley clamp
Photogate clamp
Figure 6 Pulse Mode (Method 2)
Figure 5 Pulse Mode (Method 1) and Pendulum
Mode
Figure 7 Gate Mode
Timing with a Photogate