• You will use two carts
and two motion detectors today. Place a motion detector at each
end of the track facing the middle of the track. One cart should
have a plunger; they each should have two Velcro tabs on one
bumper. One cart should have one or two masses attached.
The cart without the mass(es) attached should be on the left (Cart
A). The track should be level, such that when you place the carts
on the track at rest, they stay at rest. It doesn’t matter if you
start with the plunger extended or retracted. The plunger (or
Velcro tabs) should face the other cart. Open today’s
Logger
Pro
file.
• When a mass balance is free, determine the masses of your
carts. Record the masses in the yellow boxes of the tables, with
the units in square brackets. For the more massive cart, you will
have to hang additional mass on the balance in order to obtain an
accurate value. Next to “Collision:” on the tables of the
worksheet, type a short description of which collision the table will
be, e.g. “with plunger” or “with Velcro.”
• With Cart A (without masses) at about 20 cm in front of
the left-hand
sensor and Cart B (with masses) in the center of the track, gently give
Cart A a momentary push while acquiring velocity data. Please
prevent Cart B from crashing into the right-hand motion detector.
• You shall see sudden changes in the v(t) traces that represent
the change in velocities during the collision. Measure the
x-components of the velocities of
Carts A and B just before and just after the collision. Use the
statistics function ("STAT") on the upper toolbar, setting the brackets
around ten to fifteen datum points. Record the mean values of the
x-components of the velocities in the yellow boxes of the table, where,
for example, v
Ai
is the
initial x-velocity of Cart A and v
Bf is the final x-velocity
of
Cart
B.
Indicate the direction of motion with the convention that motion to the
right is positive. Paste your graph into the appropriate box on
the worksheet such that its width is roughly half the width of the box
and the data and data boxes are readable.
• If your first data acquisition was with the plunger extended,
depress it now, and vice-versa if your first run was with the plunger
retracted, such that the Velcro kept the carts together after the
collision. Directly above the plunger is a release pin for
extension and an oval catch to hold down as you push the plunger in.
• Repeat the data collection, and then move on to Part III,
Analysis.