LAB - THE TICKER TIMER
Overview
In many motion experiments, measurements must be taken during very short time intervals. Since
these measurements are difficult to do in "real time," mechanical timers are often used to make a
permanent record of the motion that can be measured after the actual event is over. One such
mechanical timer is the Ticker Timer.
Exercise A - Checking the Calibration of Your Timer
Materials: Ticker Timer
Carbon Disks
Timer Tape
Stop Watch
1. Secure your timer to the table so that it does not vibrate or move when it is on.
2. Prepare your timer for a recording.
 Place a carbon disk face up on the center pin.
 Thread a 2 m piece of timer tape through the guides so that it passes over the carbon disk.
3. Take a timed reading.
 One person should pull the tape through the guides
 Once the tape is moving, the other person should start the stop watch and turn on the timer at
the same time.
 Stop the stop watch and the timer at the same time. Be sure to stop the timer and watch before
the tape runs out of the guides.
 Write the time lapsed on the beginning end of the tape.
4. Gather the raw data.
 Repeat step 3 until you have 10 tapes.
 Count the intervals on each tape and write it on the end of the tape..
 Record the time and interval count for each tape in Table 1.
5. Analyze the data
 Calculate and record the average period of the timer for each tape. (Period is defined as the
amount of time for one event to happen. In this lab, the period of the timer is the amount of
time for one interval on the tape.)
 Calculate the overall average period of the timer.
 Obtain the accepted period of the timer from your instructor.
 Calculate the relative percentage of error for your measurements.
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Exercise B - Analyzing Constant Motion
Overview
Many motions that we assume to be constant (and actually appear to be constant) in reality are not.
During this phase you will gather and analyze data on an object moving at constant speed.
Materials: Ticker Timer
Carbon Disks
Timer Tape
Stop Watch
1. Secure your timer to the table so that it does not vibrate or move when it is on.
2. Prepare your timer for a recording.
 Place a carbon disk face up on the center pin.
 Thread a 2 m piece of timer tape through the guides so that it passes over the carbon disk.
3. Record a moving object.
 Attach the end of the ticker tape to your waist.
 Have your partner start the timer.
 After the timer has started, walk at a constant speed of 0.5 m/s until all of the tape has run
through the timer. Stop the timer
 Write your name on the beginning end of the tape.
4. Analyze the data.
 Mark the first dot 0 (zero).
 Since the accepted value of the timer's period is 1/60 s, mark every 6th dot, thereby marking each
1
/10 s.
 Make a 3 column data table in your lab journal and label the columns Time, Interval Distance,
and total Distance respectively.
 Measure each 1/10 s interval and record this distance in column 2. Calculate a running subtotal
in column 3.
 Plot a d vs t graph using the data from column 3.
 Plot a v vs t graph using the data from column 2.
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Questions & Conclusions (Attach typed answers)
1. Would your value for the period of the timer have been more accurate if you had drawn 5 m of tape
through the timer?
2. Would your value for the period of the timer have been more accurate if you had drawn the tape
through the timer faster? slower?
3. How much time would be "missing" if a measurement of one year was under by your relative
percentage of error?
4. Is there anything that could make the period of the ticker timer vary from the accepted value?
5. Did you achieve the assigned task of walking at 0.5 m/s? Include R%E information in your answer if
relevant.
6. Why does the data in column 3 yield a d vs t graph?
7. Why does the data in column 2 yield a v vs t graph?
8. What is the significance of the slope of the d vs t graph? Explain.
9. What is the significance of the slope of the v vs t graph? Explain.
10. If you had indeed walked at constant velocity, what shape d vs t and v vs t graphs would you expect?
Were yours'? Explain any variance.
11. Pick a time on your d vs t graph and calculate your velocity at that time. Compare / contrast this
value with the data plotted at that time on your v vs t graph. Repeat for 2 more times.
12. Cite all systematic errors that could exist in your timer setup.
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Table 1 - Checking the Calibration of a Timer
Tape #
Time (sec)
# Intervals
Period (sec)
1
2
3
4
5
6
7
8
9
10
Average
Accepted Value
R%E
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