PASCO ME-9215B Photogate Timer - Manual (Page 14)

10
Photogate Timer 012-06379B
®
g
Set the Photogate Timer to GATE mode. Now move the ball to a starting point somewhere
on the ramp. Mark this starting position with a pencil so you will be able to repeat the run,
starting the ball each time from the same point. Hold the ball at this position using a ruler or
block of wood. Press the RESET button. Release the ball so that it moves along the ramp
and through the photogate. Record the time in Table 3.1.
h
Repeat the trial at least four more times with the same starting point, and record your times in
the table.
i
Measure the distance from the point directly below the ramp to each of the landing spots of
your ball. Record these distances in the data table.
Data and Calculations
c
Take the average of your measured times and of your measured distances. Record these aver-
ages in the data table. Also record the average distance as d
x
in the space provided to the right
of the table.
Table 3.1
Data from Photogate Timer
Trial Time Distance
1
2
3
4
5
Averages
v
0
(avg)
Δ Δ Δ Δ Δd =
Vertical height, d
y
=
Average horizontal distance, d
x
=
Horizontal velocity, v
0
=
Percentage difference =
d
Divide
Δ Δ Δ Δ Δd by your average time to determine v
0
, the velocity of the ball just before it left the
table.
e
Now determine the horizontal velocity of the sphere using the equations for projectile motion
and your measured values for d
x
and d
y
:
d
x
= v
0
t; d
y
= 1/2 at 2 ;
where a equals the acceleration caused by gravity (9.8 m/s 2 or 980 cm/s 2 ).
f
Compare your two values for v
0
. Report the two values and the percentage difference.
Optional
If you have time, choose a value for d
x
and a value for d
y
. For what value of v
0
will the ball
travel the distance d
x
as it falls the distance d
y
? Adjust the height and angle of the ramp and the
starting point until you produce the predicted value of v
0
. Now run the experiment to see if
your calculated values for d
x
and d
y
are correct.