012-04840E
Dynamics Cart
12
®
Procedure
1. Stand the Dynamics Cart on its end so that the spring plunger is aimed up, as shown in
Figure 4.1. Using masking tape or rubber bands, fix a ruler to the cart and adjust it so that
the 0 cm mark on the ruler lines up with the upper surface of the plunger. Take care to avoid
parallax errors!
2. Carefully add enough mass to the top of the plunger so that it is nearly fully depressed.
Record this mass and the corresponding compression
x
(initial position) of the spring in
Table 4.1.
3. Remove approximately one quarter of the mass used in step 2. Record the new mass and
x
values in Table 4.1.
4. Repeat step 3 until no mass remains on the plunger.
5. Plot a graph of
F versus x
using your data and determine the slope of the best line through
your data points. This slope is the spring constant for your cart. Show your slope calcula-
tions on the graph and record
k
below.
6. Determine the mass of the cart using a mass balance and record this value below.
7. Using
EQN-3
and your values for
m, x
o
(i.e. the compression of the cocked spring) and
k
,
predict the launch velocity of your cart and record this below.
8. Cock the spring plunger to the value of
x
o
that you have chosen; then place the cart in its
starting position and launch it. Using a stopwatch and a meter stick, determine the average
range
d
and the average total time spent rolling
t
. Record these below.
NOTE:
To avoid reaction time errors, the person who launches the cart should also time
the cart’s motion.
9.
Using
EQN-4
, determine the observed value of
v
o
and compare it with the predicted value.
Data and Analysis
N
m
s
m
s
m
Mass of cart =
_________
kg
k =
________
x
o
=
________
m
Predicted value of launch velocity v
o
=
__________
Average d =
_________
m Average t =
__________
sec
Observed value of the launch velocity v
o
=
__________
Percent (%) difference between observed and expected values of v
o
=
__________
Summary of Contents for ME-9430
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