PASCO ME-6950 PAScar with Mass - Manual (Page 13)

012-07361B PAScar with Mass
12
Procedure
1. Stand the PAScar 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 car 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 car. Show your
slope calculations on the graph and record k below.
6. Determine the mass of the car 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 car and record this below.
8. Cock the spring plunger to the value of x
o
that you have chosen, then place the car 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 car should also
time the car’s motion.
9. Using EQN-4, determine the observed value of v
o
and compare it with the predicted
value.
Data and Analysis
Mass of car = _________ 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
= __________
% Difference between observed and expected values of v
o
= __________
s
m
s
m