Determining the Pop Time of a Toy Popper
(1 Class Period, Groups of 3)
Objective
In this experiment, we will be revisiting the measurements we made when we attempted to
calculate the force and time of a toy popper’s pop. This experiment will allow us to compare our
previous results with direct measurements of the event using a LabQuest handheld computer and
a force probe. We will then calculate the error in the time and force from the two sets of data.
Background
The LabQuest handheld computer is able to collect 1000 data points per second and make
complex calculations. We will use these features to find the actual time and force of the “pop.”
The calculation for error is as follows:
(Experimental - Accepted)
Relative Error =
 100%
Accepted
Assume the results from the LabQuest are the accepted values and the data derived from the
height calculations are the experimental values.
Materials
 LabQuest Handheld computer
 Dual-Range Force Sensor
 Toy poppers



Two meter sticks
Ring Stand
Hanging scale platform
Procedure:
1. As in the previous experiment, place the popper on the table and accurately measure the
height using the two meter sticks. Do this at least three times and average the height. Once
you have determined the height, you can calculate vi using vi  2gh .
2. Measure the height of the popper ( h p ). Determine the average velocity of the popper,
vavg 
a
3.
4.
5.
6.
vi
vi  v f
2
, then calculate the time of the pop with t pop 
hp
vavg
. Calculate the acceleration
. Use a gram scale to get the mass of the popper (remember to convert the grams into
t pop
kg) and calculate the force of the pop using the formula F  ma .
Use a hanging platform or make one by cutting a 3”-4” square piece of foam board. Use
string to make three supports and tie them into a knot at the top. Tie a second knot about 1/2”
below the first one. This upper loop will stop the platform from falling over.
Unscrew the bar of the ring stand and place it flat on the table so that it hangs over the edge
towards you. You may want to place a book on it to keep it from rolling. Hang the DualRange Force Sensor on the bar so that the hook is hanging down. Now attach your platform
onto the hook of the sensor.
Turn on your LabQuest and plug the Dual-Range Force Sensor into Channel 1 on the top of
the device. Make sure the 10N range is selected on the sensor. Zero out the sensor with the
platform attached.
Click “Sensor” then “Data Collection.” Under Timing, set Rate to 1 sample/ms, Length 30
ms. Enable Triggering, select “Start collecting when the sensor is increasing across 2.0 N,”
and enter “Collect 20 points before trigger.”
7. Press the button to start collecting data, then invert the popper and place it on the platform.
The LabQuest will wait for the triggering event. When it pops, you will have collected the
event on the LabQuest.
8. Highlight the event from the beginning of the pop to the end of the pop. Select “Analyze,”
then “Statistics” and “Force.” You will be able to read the maximum force of the pop from
the screen. Read the time from the bottom of the screen, this is the LabQuest – tpop in your
chart. You will also need this for step 11.
9. Record the maximum force from the display and the duration of the pop on your chart.
10. Print the graph and include it in the lab report.
11. The Impulse we were studying can also be read directly from the LabQuest. Select the
section of the curve that begins the event and returns to the same level. Select “Analyze,”
then “Integral,” and then “Force.” The number you get on the screen for the integral is the
impulse, which is the force (in Newtons) times the time (in milliseconds). Divide the integral
value by the mass (in kg) to calculate the vi of the pop.
12. Repeat the experiment from the beginning with a different size popper. If you are using one
of the mini poppers, you will need to lower the triggering force to 0.25 N for the small popper
to trigger the LabQuest.
13. In the analysis section, create the table below. Calculate the error for the initial velocity,
time and maximum force. This is the force value that you found determined from the height
of the pop. On the LabQuest, this is the value from the statistics, not the average force from
the integral.
Large Popper
Small Popper
Height
Experimental - Vi
Experiment - tpop
Experiment – Force
LabQuest – Vi
LabQuest - tpop
LabQuest – Force
% Error – Vi
% Error - tpop
% Error - Force
Make sure you show sample calculations and explain every one of your steps. Pay
attention to significant figures.
Questions
1. Explain why the average force is different from the peak force read from the screen.
2. Can we measure the time of the pop using a stop watch? Why or why not?
3. What could you have done in this lab to improve the accuracy of your results?
4. What should be done to improve this lab for next year’s students?
Lab Report Checklist:
 Headers are filled in completely
 Introduction
 Material & Procedure
 Data & Observations
 Analysis





Conclusion
Report is neat, spelling is correct
Units are included where needed
Correct significant figures used
Signed on the last page