Objective: To be able to…
 analyze displacement and time data to determine whether motion is
uniform.
 relate the slope of a position v. time graph to the mean of a velocity v. time
graph.
 determine based on the data plot lines on a position v. time graph which of
two data runs is faster.
Safety: Take care not to release the car’s plunger in such a way that it strikes a
person or lab equipment.
Procedure:
1. Set up your PASCO system like this and open the file “03: Velocity.” Note: Be
sure that the motion sensor is at the 0.00m end of the track.
Motion
Sensor
Car
Track
2. Time to experiment! Assign one person to run the computer and one person
to start the car…and one person to brace the motion sensor so that it doesn’t
fly off the track when the car hits it. Then…
a. Push the plunger into your car so that it clicks two times.
b. Position your car at the end of the track opposite from the motion
sensor.
c. Press “Start” to start monitoring data on your computer. You should
hear a clicking noise from the motion sensor. If you don’t, call your teacher
over. (Note: You don’t have to release your cart immediately upon
pressing start. You’ll be able later to disregard the data that the computer
collects before the car moves.)
d. Press the plunger to release the car.
e. Press “Stop” to stop timing at some time after the car reaches the
motion sensor.
3. Look at the top graph (Position v. Time).
a. Place the Smart Tool on the data plot so that the y-value of the (x,y)
ordered pair is 0.900m. This is the point that represents when the car
was located at the 0.900m (or 90cm) mark on the track.
b. Use the Delta Tool and move it to the point on the line representing
when the car’s position was at 0.800m. The vertical side of the box
shows the displacement, or change in position, of the car from 0.900m
to 0.800m, which is -0.100m. The horizontal side of the box shows how
long it took the car to move between those points. (In the example
below, it took the car 0.1157 seconds to move from 0.900m to
0.800m.)
c. Find the time intervals for every 0.100m displacement between 0.900m
and 0.200m.
Open an Excel spreadsheet so that you can create a data table. Your data table
should allow you to record the time it took the car to travel between every 0.100m
position interval from position 0.900m through position 0.200m. (For example:
from 0.900m to 0.800m, from 0.800m to 0.700m, etc.) It is up to you to decide
how to arrange this table, although please keep in mind that a good data table:
 …is easy to read.
 …has the variables that are being presented clearly labeled.
 …has the units for those variables clearly labeled.
 …matches the precision of the original data. (This means all the
numbers in the table should have the same number of digits as the
computer.)
 DO NOT CLEAR THE COMPUTER
SCREEN UNTIL THE LAB IS OVER! 
4. Now click and drag the mouse on your computer screen over the part of the
graph that shows when the cart was moving from position 0.900m to position
0.200m. This will highlight the relevant part of the graph. Then call your
teacher over to check that you’ve highlighted the right part.
5. Click on the “Fit” box and select “Linear Fit.” Look in the box that appears and
record the slope of the graph for this highlighted part, which is the only part in
which you’re interested. Also record the uncertainty and use proper units (yaxis units/x-axis units.)
6. In the bottom graph (velocity v. time) highlight the data for the same time
period. Record the mean velocity of this highlighted region near your other
data. Be sure to record units.
 DO NOT CLEAR THE COMPUTER
SCREEN UNTIL THE LAB IS OVER! 
7. Without clearing the computer screen () repeat steps 4-6, this time pressing
the plunger in so that it clicks three times. Record the Position v. Time slope
and the Velocity v. Time mean over the 0.900m to 0.200m displacement as
before in new data tables. (Note: You are only returning to step 4, not all the
way to the beginning. No need to find the time intervals for this run.)
8. Remove highlighting and linear fit boxes from your data screen. Zoom so that
all of the important data from both runs is visible in each graph without
showing too much of the extra, irrelevant data lines. Take a screen shot of the
graph with the data lines still on it. Save this screen shot in a Word document
so that you can insert it later in to the lab report.
Data Tables & Graphs: This section should include:
 Position Interval vs. Time data table for run one with plunger pushed in
two notches
 Slope value for run one with plunger pushed in two notches
 Mean value of velocity for run one with plunger pushed in two notches
 Slope value for run two with plunger pushed in three notches
 Mean value of velocity for run two with plunger pushed in three notches
 Image of computer screen showing graphical representation of data
Data Analysis: No calculations required for this lab
Conclusion: Write a conclusion summarizing what the results reveal about the
objectives of the lab.
Comments: State any comments you have about your experience with this lab.