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.”
Motion
Sensor
Car
Track
2. Time to experiment! Assign one person to the computer and one person to
start the car…and one person to catch the car just before it hits the motion
sensor.  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. Time to collect data! For now you should jot this data down on paper,
although later you’ll type it into Excel and insert it into the “Data Tables &
Graphs” portion of typed lab report. Your data table should allow you to
record the time it took the car to travel between every 10cm position
interval from position 90cm through position 20cm. (For example, from
90cm to 80cm, from 80cm to 70cm, 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.)
To collect the data, look at the top graph (position v. time). You’ll need to
find initial and final times for each interval and subtract to find the time it
took the car to travel from one position to the next position 10cm farther
down the track.
a. Use the Smart Tool to find the time at the beginning of the car’s
motion. This will be t1.
b. Use the Smart Tool to find the time (t2) at the first checkpoint position.
Then use the formula t = t2 – t1 to find the time it took for the car to
reach this position from when you pressed the plunger.
c. For each successive position, t2 will become the new t1, and you’ll have
to use the Smart Tool to find the new t2.
t2
t1
 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 90cm to
position 10cm. This will highlight the relevant part of the graph. Then call
your teacher over to check that you’ve highlighted the right part.
5. Then click on the “Fit” box and select “Linear Fit.” Look in the box that
appears and read the slope of the graph. This shows the slope only over
the highlighted part, which is the only part in which you’re interested.
Record this slope clearly near your data table when you write your lab
report. Be sure to use proper units (y-axis units/x-axis units.)
6. In the bottom graph (velocity v. time) highlight the data for the time period
during which the car traveled from 90cm to 20cm. Record the mean
velocity of this highlighted region near your other data. Be sure to record
units.
7. Do not clear the computer screen. Repeat steps 4-6, this time pressing the
plunger in so that it clicks three times. Record all of your data as before in
new data tables. (Note: You are only returning to step 4, not all the way to
the beginning.)
 DO NOT CLEAR THE COMPUTER SCREEN UNTIL THE LAB IS OVER! 
8. Remove highlighting and linear fit boxes from your data screen. Do a
screen shot of the graph with the data lines still on it. Save this screen
shot so that you can insert it later in to the lab report.
Data Tables & Graphs: (12 points) 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.