Plug in the sensor
Connect the USB cable from the sensor to the laptop
Set up the track and cart
Place the track on a level surface, either the floor (if you can find room)
or the table. Attach the Motion Sensor to the left end of the track. The other
end has a "bumper" to keep the cart from flying off the end. It also
has a screw you can use for leveling the track. You should verify that it is
level by using the cart. Aim the Motion Sensor so the beam will be parallel
to the track.
Start up the software
Open LoggerPro (the red diamond with a caliper over it). There should be displayed
graphs of position and velocity. (These are really graphs of the x components
of the position and velocity vectors.)
Take some data
Click the green Start button to beginning collecting data. You should hear some
clicks from the Motion Detector. Roll the cart back and forth on the track,
verifying from the graphs that the sensor is “seeing” it. You may
need to adjust the beam up and down. Click the Stop button to stop collecting
data. You can erase this set of data by choosing Clear Lastest Run from the
Experiment menu.
Using the software
You can adjust the graph axes by dragging the axis lines left or right. By dragging
on the numbers along the axes you can adjust the graph scale.
You can find the slope of part of a graph by dragging a box around data points
you want to use, and then clicking on the Fit button at the top of the graph.
You can choose the kind of curve you want to fit. To save a picture of a portion
of the screen (like a graph) press Shift-Apple 4, then drag a box around the
area you want to capture. The file containing the picture is automatically saved
to the desktop.
Things to investigate
Explicitly connect what you see here with what is seen with the fan cart movies
analysis and the VPython simulation.
Situation 1: Initial Push by Hand
Without recording data on a level track, with the fan turned off, gently push
the cart. After discussion with the group, have the recorder sketch predictions
of what the following plots look like:
After, repeat the experiment and record the x and Vx data. Compare with your predictions.
Redo the above steps with one end of the track proped up with a book.
Situation 2: Forward Push by Fan
Without recording data on a level track, starting from rest with the fan turned
on, release the cart. After discussion with the group, have the recorder sketch
predictions of what the following plots look like:
After, repeat the experiment and record the x and Vx data. Compare with your predictions.
Situation 3: Backward Push by Fan
Without recording data, with the fan pushing against the motion, push the cart
(not hard enough to go off the end). After discussion with the group, have the
recorder sketch predictions of what the following plots look like:
After, repeat the experiment and record the x and Vx data. Compare with your predictions.