• Open the
Logger Pro
file and
the worksheet
for today. The switch on the force plate should be
on the lower range setting, -200/+850 N. Choose a ball that you
can drop onto the force plate and record at least five distinct bounces
on the F(t) graph. Measure its mass. If you need to put
something on the mass balance to keep the ball from rolling off, make
sure to subtract its mass. Record the mass of the ball on the
worksheet. Also type a short description of the ball.
• Place the ball on the force plate and
zero the force using the Zero function on the upper Logger Pro toolbar.
Then raise the ball above the plate by about one meter and drop it
while
acquiring data. Record the times of the first five consecutive
bounces in the table in the appropriate boxes of the worksheet.
• Zoom into the data for the second bounce. You’ll see a
collection of peaks. The entire first peak plus the first half of
the
first valley is a good measure of the impulse of the impact. Use
the Integral function to obtain the impulse J
y2
of the
impact and
record it in the J
y2 box. Repeat the
integration for
the third
and fourth bounces and record J
y3 and J
y4.
• Zoom back out to where your graph shows the five bounces plus
the data boxes for the integrations for the second, third, and fourth
bounces. Copy and paste this graph into your worksheet, ensuring
that the data boxes are readable. You might need to decrease the
size of the graph, such that the data boxes consume a larger portion of
it.
• Calculate the parameters associated with the green boxes of the
table in the worksheet: the ball’s speed v
i,i-1,
its
change in
y-momentum p
yi, and the ratio of the change in y-momentum to
the
integral
of force over time p
yi/J
yi. Then find the
average, sample standard
deviation (defined in
Part II of
the friction experiment), and fractional uncertainty (sample
standard deviation
divided by
the average). Your fractional uncertainty should be less
than 0.100.
• Check that you filled in all of the square brackets in the
table with the correct units.
• The last question on the lab report asks you to report your
result in
standard form and, in your
own words, discuss what you
expected in comparison to your experimental result. Mention
possible reasons for any difference.