012-06379B
Photogate Timer
7
®
Experiment 2: Kinematics on an Inclined Plane
EQUIPMENT NEEDED:
-Photogate Timer
-Meter stick
-Ball and ramp, [A ball bearing (approximately 1.8 cm diameter) and a U-channel
ramp (approximately 50 cm long with an inside width of approximately 1 cm) will
work well, but the exact dimensions are not important].
Introduction
In this lab you will investigate how the velocity
of an object varies as it undergoes a constant
acceleration. The object is a ball rolling down
an inclined ramp. Instead of the usual investiga-
tion of velocity as a function of time, you will
measure its velocity as a function of the distance
it has travelled from its starting point.
(
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➤
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Note:
This experiment is just as easily per-
formed with a glider on an inclined airtrack.)
Procedure
c
Set up the apparatus as shown in Figure 2.1.
d
Move the ball slowly through the photogate, using the
meter stick as shown in Figure 2.2. Determine the point
at which the ball first triggers the Photogate Timer—this
is the point at which the LED on top of the photogate
first turns ON—and mark it with a pencil on the side of
the channel. Then determine the point at which the ball
last triggers the timer, and mark this point also. Measure
the distance between these marks and record this dis-
tance as
Δ
Δ
Δ
Δ
Δ
d
. Determine the mid-point of this interval,
and mark it in pencil on the side of the channel.
e
Set the Photogate Timer to GATE mode and press the
RESET button.
f
Move the ball to a point 5 cm along the track above your mid-point. Hold it at this
position using a ruler or block of wood. Release the ball so that it moves along the
ramp and through the photogate. Record the distance travelled (from the starting point
to the midpoint) and the time (t
1
) in Table 2.1.
g
Repeat the trial 3 times so you have a total of four measured times, then take the aver-
age of your measured times. Record your results in the table.
h
Move the ball to positions 10, 15, 20…40 cm from the midpoint, and repeat steps 3-5.
Data and Calculations
c
For each distance from the midpoint of the photogate, calculate the final velocity of the
ball by dividing
Δ
d by your average time.
d
Construct a velocity versus distance graph, with distance on the horizontal axis.
Ball
Ramp
Fig-
Mark with a pencil
on side of channel.
Meter Stick
Figure 2.2: Measuring
Δ
Δ
Δ
Δ
Δ
d
LED goes OFF
LED comes ON
Photogate
Timer
