• As for
the previous experiment, place the cart on the track, putting its
wheels in the slots. Check that the track's feet are positioned
at 60 cm and 160 cm and adjust them if necessary. The computer
should be connected to an interface box, which in turn should be
connected to a motion sensor. Place the motion sensor on the left
end of the track. The face of the sensor should be
vertical. Put masses or other objects beneath the left-hand feet
of the track such that the left-hand end is elevated by a few
centimeters.
•
Practice giving the cart a push from the right-hand end of the track
such that it moves at least halfway up the track, but reaches no closer
than 20 cm from the sensor. Please catch the cart before it
crashes into the stopper at the end of the track.
•
Open today’s Logger
Pro file, and start the motion detector by clicking the
green Collect Button up on the Logger Pro tool bar (or, alternatively,
just press the space bar). You can Autoscale the graphs with the
“A”
button in the top ribbon of the Logger Pro window. It is likely
that parts of your graphs are neither interesting nor relevant.
For example, the cart might have been sitting at rest for several
seconds, or there might be glitches in your data. With the
cursor,
highlight the bad parts of one of the graphs. You’ll see the
corresponding parts of the other graphs highlighted as well. The
Data Browser is on the left-hand side of the Logger Pro window.
Scroll down the browser until you see the highlighted data that
corresponds to what you have highlighted on the graphs. Under the
Edit menu, select Strike Through Data Cells. You’ll see the data
disappear, both in the browser and on the graphs.
•
Your x(t) and vx(t) data should be free of noise, although
your ax(t)
data might be noisy. Now is the time to ask your lab instructor
for help if your data are poor or if you are not confident of how they
should appear.
•
Reflect for a moment. Do you understand why the curves look the
way they do? Why is the x(t) graph a parabola, and why is the
vx(t) graph more-or-less linear? Can you guess why the
vx(t)
graph has two slightly different slopes? What would happen to the
curves if the track were tilted the other way?
With your
equipment properly set up and your understanding of the graphs sound,
it is time to learn about more sophisticated aspects of Logger Pro as
well as the relationships among the kinematical variables. Please
click on the link to Part II.