Studying Poppers - Computer
A "Popper" is a toy that consists
essentially of half a handball/raquetball. Users "invert" the
Popper by pressing on the top, then place it upside down on a
surface. As the Popper returns to it's normal shape, it exerts a
force on the surface which then exerts an equal and opposite
force on the Popper. This force pushes the Popper upward and
launches it into the air.
In this experiment you will investigate and characterize the
force that a Popper makes on the surface as it lifts off. Using
the data you obtain, you will work with additional concepts
including impulse, momentum, kinetic and potential energy.
Preparing for Data Collection
- Vernier Dual-Range Force Sensor (DFS-BTA), Vernier
computer interface*, Wood platform, Popper(s)
* Appropriate interfaces include
LabPro, LabQuest Mini, LabQuest 1 and 2, and Go! Link
- Remove the hook in the end
of the force sensor. You'll find the thread is a standard one
(6-32). Cut a square piece of wood (or plywood) that's a bit
bigger than the popper and drill a hole in the center that
will allow a 6-32 bolt to go through. Fasten the wood platform
to the sensor, then remove the thumb screw on the other end of
the force sensor, the one that can be used to hold it to a
- Set the force sensor to the 50-N setting. Plug the interface
into the computer, connect the force sensor to one of the
analog inputs, and launch Logger Pro. Set up an experiment
file with a high collection rate (≥ 200 samples/s), but a
short collection time (0.1 second). Enable triggering and set
it so collection starts when the force exceeds a minimum value
of 5 N. Also collect 10 samples before triggering. Save this
file so you can make changes as needed to fine tune it and so
you can use it again next time.
- In practice, you'll hold the end of the force sensor firmly
against the table with the wood platform on top as shown in
the diagram to the right. Go to Experiment > Calibrate
Sensor > Dual-Range Force Sensor. With
nothing on the platform, set the value to "0" N and click on
"Keep" when the voltage is stable. Put a 500-g mass on the
platform, enter "4.9" N and click on "Keep" when the voltage
is stable. Indicate [Done]
at this point. Set the popper on top of the platform, then
zero the force reading. Measure and record the mass of the
Popper in the Data Table that follows.
- One lab partner
will hold the force probe steady against the table. A second
partner, the computer operator, will start data collection.
The screen should show something like "Waiting for data". A
third partner, the popper operator (!), inverts the popper to
store up elastic energy, places the popper on the platform,
then gets ready to catch it. A fourth partner should be
positioned to determine the maximum height of the Popper after
it lifts off. Record that value in the Data Table.
- When the popper
unfolds, it pushes down on the platform, triggering data
collection. Note that the force is not constant, but you get a
nice graph showing force vs time. Another thing shown is the
ringing of the sensor. The mechanism inside is similar to a
bell that is tapped and it keeps vibrating for a short time.
- If your graph
looks "chunky", you might consider increasing the collection
rate. You can go as high as 1000 samples/s with modern
computers with no problem. Once you have a good graph, this is
the one you will work with in this lab.
- Determine the
area under the graph for the time while the force is
positive. A sample is shown here. This is the impulse.
Record it in the Data Table that follows. Approximately how
long was the Popper pushing down on the platform? What was
the average force during that time?
- How much
momentum did your Popper gain during it's liftoff? What is
your calculated liftoff speed given the measured mass of the
- With this speed,
how much kinetic energy did your Popper have when it lifted
- How much
potential energy should your Popper have when it reaches the
top of it's trajectory? How high should the popper have gone
before it stopped rising? How does this number compare with
the measurement you made during the experiment?
- Repeat your work
and compare the second set of data with the first.
- Summarize the
performance of your Popper in a coherent paragraph citing
data and calculations from your lab.
- Place a
measuring device such as a meter stick near where the Popper
will be launched. Position a high-speed video camera so you
capture an image of the popper as it reaches the top of it's
trajectory. Compare this result with the one that is
calculated from the impulse data.
- Set up a video
camera so you can capture the initial launch of the Popper
from the platform. You may only get 2-3 images, but from
these, determine the liftoff speed. A measuring device such
as a meter stick should be in the image for scale. Use the
video analysis capability of Logger Pro to obtain this
value. Compare the video value to the calculated value from
the impulse data.
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