Lab 1C Constant Velocity Observations
Purpose:
The purpose of this lab is to gain experience with different objects traveling at a
constant velocity and to recognize and analyze the motion graphs associated with this
motion.
Method:
Students will be performing many experiments measuring the distance and time
for different objects all traveling at a constant velocity. Students will then display the
information on graphs and analyze this information.
Hypothesis: Sketch what you think a time vs. distance graph for constant velocity would look like.
Include your reasoning.
Vocabulary: speed
Materials:
velocity
marble
meter stick
PVC tube
timing device
laptop computer with motion detector
ring stand
Procedure A: Marble on track
1. You will be collecting data for time and distance for the constant velocity of a marble
leaving a track elevated 10 cm and then repeat the whole experiment for the track
elevated 20 cm.
2. What will you use as your independent variable? Dependent variable? Which would
lead to more accurate results – controlling the distance or controlling the time? Try
both ways and decide on the best way to run your experiment.
3. How many different data points will you be measuring (the more you have the more
accurate your best fit line becomes)?
4. How many times will you repeat the measurement for each data point (collect several
times and take the average)?
5. Decide when you will be starting and stopping the timing device.
5. Write a procedure and construct data table(s) in your lab book.
6. Perform your experiments and collect your data.
Analysis A: Marble on track
1. Graph the data for the two experiments on one graph (two colors & a key).
2. Calculate the slope and y-intercept for each height.
3. Write the equation of the best fit line for each height.
Conclusion A: Marble on track
1. Compare the slopes and y-intercepts for the two lines. Be as specific as possible.
2. Sketch (no scales on axes and no specific plotted points) what a distance vs. time
graph for the marbles would look like (refer to the marbles graph already
constructed). Remember to label the lines.
3. Referring to the original graphs made, calculate the slopes for the distance vs. time
graph lines for both marble lines sketched in #2.
4. Describe what these slopes of the lines represent.
Procedure B: Use graphing calculators to graph data & make calculations
1. Enter data into calculator:
<STAT>
<Edit>
Clear out old data by highlighting <L1> <clear> <enter>
Enter x data into L1
Enter y data into L2
2. To plot data:
<2nd>
<STATPLOT>
<Enter>
Set calculator as shown:
3.
Enter
numbers
that makes
sense for
your data
4.
5.
6.
7.
To set window size:
<window>
Xmin =
Xmax =
Xscl = 1
Ymin =
Ymax =
Yscl = 1
Xres = 1
To graph:
Clear any previous best fit lines by <y=> <clear>
<graph>
To get the equation of the best fit line:
<stat> <calc> <4> L1,L2 <enter>
To graph the equation of the best-fit line:
<y=>
Enter equation rounding to a reasonable number into y1
<graph> your line should pass through your data
To graph 2nd set of data put data into L3 and L4, turn on Plot2, use a different mark,
get the best fit line using L3,L4 and input equation into y2, don’t forget to change
window if necessary
Analysis B: Use graphing calculators to graph data & make calculations
Use calculator to calculate the equation of the best fit line for each set of data and
calculate your % error for each of your slopes.
Show the calculator with the graph to your teacher.
Procedure C: Graphs on laptop computer with motion detectors
Part A:
1. Sketch the graphs for this section in your lab book leaving space next to each
for a description of how to walk. (don’t forget to number and title each graph).
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2. Examine the first graph and discuss the motion without using the computer.
Do not use the term “acceleration” in any of your descriptions. Instead, use
terms and phrases such as, “rest”, “constant speed”, “speed up”, “slow down”,
“toward sensor” and “away from the sensor”. Write a hypothesis that is a specific
description of the motion.
3. Repeat for all graphs.
4. Carefully plug a sonic ranging device (motion detector) into a laptop and then open
up the logger pro program. Open up the folder “Physical Science with Vernier” and
the file “35a Graphing your motion”.
5. Position the sonic ranger so that its beam is about chest high and aimed
horizontally.
6. The computer should be set to graph position vs. time. Initiate the sonic ranger by
pressing collect on the computer and note how close and how far you can get before
the readings become unreliable.
7. When you are ready, initiate the sonic ranger by pressing collect on the computer and
move so that your motion generates a similar graph. Always move with your back
to the sensor so you have a sense of forward and backwards motion. Write a
description of the motion next to the sketch of the graph in your lab book.
6. Make sure each person in the group can move to match this graph before moving on
to the next graph.
Analysis C: Graphs on laptop computer with motion detectors
1. Write the descriptions below in your lab book then make a graph that you think
corresponds to the description.
a. Move toward the sensor at constant speed, stop and remain still for a second,
then walk away from the sensor with constant speed.
b. Move toward the sensor with decreasing speed, then just as you come to rest,
move away from the sensor with increasing speed.
c. Move away from the sensor with decreasing speed until you come to a stop.
Then move toward the sensor with increasing speed.
Conclusion C: Graphs on laptop computer with motion detectors
1. How does a distance vs. time graph show the difference between forward
motion and backward motion?
2. How does a distance vs. time graph show the difference between slow motion
and fast motion?
3. How does a distance vs. time graph show the difference between constant motion
and speeding up or slowing down?
4. Sketch each graph in your lab book and describe what is happening in each one of the
following graphs.
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Procedure D: Graph of nonuniform motion
1. Construct a distance vs. time graph for the following data on a full page. Describe the
meaning of this data.
Time(sec) 1
Distance 1
(m)
2.
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3
3
8
4
14
5
22
6
32
7
44
Insert tangent lines at 1 sec, 3 sec, 5 sec, and 7 sec each in a different color.
Calculate the slope of the tangent lines at 1 sec, 3 sec, 5 sec, and 7 sec.
3. What does the slope of the tangent lines represent?