The Velocity Lab
Part I: Constant Velocity
Objectives
1. Define constant velocity.
2. Collect and organize data of the car’s motion.
3. Create a position vs. time graph using data collected.
4. Define the meaning of the slope (i.e. what does it tell you about the car’s motion?)
Materials:
*Battery powered car (Anything will do here as long as it moves at a relatively constant speed.)
*Meterstick
*Stopwatch, timer, or metronome (http://www.metronomeonline.com)
*7 small pieces of masking tape
Procedure
1. Mark the starting point on the floor using a piece of masking tape. (This is the 0 cm point.) When
you begin, the front of the car should be at the starting point.
2. Start the car moving.
3. At equal time intervals (1 second, for example, but you could use any time) mark the position of
the front of the car with a small piece of masking tape.
4. Do this for at least 6 time intervals
5. Measure the displacement of all the marks from the starting point and record the data in Data
Table 1
6. Repeat for two more trials and average your distances
Data Table 1
Time, s Distance, cm Distance, cm Distance, cm Average Distance, cm
0
1
2
3
4
5
6
Graph the Data
In this lab, "Position" is the dependent variable, so should go on the y-axis and "Time", as the
independent variable goes on the x-axis.
Part II
In part I, you started the car at the reference point. If your car is at this point, then its position
is zero and every other position is measured from this point. In Part II, you will start your car
somewhere that is not at the reference point. So your initial position will not be 0 cm, but some
distance away from it. Then the car either moves further away or closer to the reference point.
1. Set up the lab as you did in Part I.
2. Start the car moving on the positive side of the reference point (either direction) and
immediately start the time on the stopwatch. Note that any measurements taken on this
side of the reference point will be recorded as a positive displacement, while any
measurements on the other side will be recorded as a negative displacement.
3. As the timer reads the time aloud, the marker will mark the position of the car on the floor
with tape. Take at least 6 data points.
4. Measure the displacement of all the marks from the reference point and record the data
in data table.
5. Repeat starting the car on the negative side of the reference point (moving in either
direction).
Record data in an organized, labelled manner:
Average
Δx
Time
Change in Position (cm)
(s)
Change in Position (cm)
1
2
3
4
5
6
7
8
Graph data with change in position on the y-axis and time on the x-axis
Average
Δx
Two posts are required to complete this lab discussion.
Post I is your initial conclusion based on the data obtained in your experiment. It should
be written in complete sentences.
*Upload a picture of each of your experimental setups. The picture must include a piece of
paper with your name and the date. (Instructions on how to do this is shown on the Lab
Discussions page.) Not having the correct pictures will result in a zero grade.
*Post one Position Time graph with a line from all three parts of the Constant Velocity Lab
Part I and Part II. (So one graph with three lines.)
*Post one Velocity Time graph with a line from all three versions.
*Describe the motion of the car for each situation. Where does it start? What direction is it
going? What is its velocity? Specifically, how does YOUR GRAPH support your description?
*Write an equation for each line on the Position Time graph. Explain what this equation
means. What is the physical meaning of the slope? y-intercept?
Post II: Respond to at least one other posted result.
Compare your results. Be specific here!
What is the same in both conclusions? Did both sets of data draw the same relationship
between the variables?
Are your graphs/equations similar? How?
What is different? (Hint: Look at the slope of your graphs) What would account for the
differences that you see?