Lab 1B 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
constant velocity buggy
meter stick
Timing device
laptop computer with motion detector
Procedure A: Constant velocity buggy
1. You will be collecting data for time and distance for the constant velocity buggy
powered by two batteries and then repeat the whole experiment for the one battery
buggy.
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 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 at each data point (collect several
times and take the average)?
5. Decide where on the buggy you will be measuring (front bumper, front tire, back
bumper, etc) and 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. The buggy may start to curve during
its travels. If this happens give it a slight nudge with a meter stick to keep it traveling
straight.
Analysis A: Constant velocity buggy
1. Graph the data for the two buggies on one graph (two colors & a key).
2. Calculate the slope and y-intercept for each buggy.
3. Write the equation of the best fit line for each buggy.
Procedure B: Constant velocity buggy with motion detector
1. 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”.
2. Position the sonic ranger so that its beam is pointed at the back of the buggy.
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Initiate the sonic ranger by pressing collect on the computer and note how close and
how far the buggy can get before the readings become unreliable.
Start with the two battery buggy directly in front of the motion detector and press
collect. The buggy may start to curve during its travels. If this happens give it a slight
nudge with a meter stick to keep it traveling straight.
Try several times until you are sure that you have a reliable graph. The graph should
be relatively smooth.
Sketch the graph the computer shows in your lab book (ignoring the little bumps and
wiggles) include a description of buggy used and starting/ending points. Use a ruler
whenever making straight lines and don’t forget to number and title the graph.
Repeat this procedure with the one battery buggy and record in your lab book.
Start with one buggy far away from the sensor and collect data as it moves towards
the sensor. Record this graph & description. Repeat with the other buggy and record.
Using the two battery buggy start with the buggy 50 cm in front of the sensor and
move away from the sensor. Record this graph & description.
Analysis B: Constant velocity buggy with motion detector
1. Compare graphs of motion moving towards the sensor (backwards) with graphs of
motion moving away from the sensor (forwards).
2. How are the steepness of the line and the speed of the buggy related?
3. What does the y-intercept tell about the buggy?
Conclusion A & B:
1. Compare the two slopes & y-intercepts for procedure A. Be as specific as possible.
2. In procedure B what would a negative y-intercept mean about the buggy?
Procedure C: Graphs on laptop computer with motion detectors
1. 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”.
2. Position the sonic ranger so that its beam is about chest high and aimed
horizontally.
3. 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.
6. When you are ready, initiate the sonic ranger by pressing collect on the computer and
keeping your back to the sonic sensor so you have a sense of forward and backward
motion, walk as described by the first graph on the next page. Observe the graph
made by the computer. Perform several times to make sure you are getting the
correct graph.
7. Record a sketch of the graph in your lab book and include the description of how you
walked. Use a ruler and number and title each graph.
8. Make sure each person in the group understands this graph before moving on to the
next graph.
9. Perform procedure for all 8 graphs.
Start away from the sensor and walk
near at a constant slow speed
Stand still
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time (sec)
time (sec)
Start near the sensor and walk
away at a constant fast speed
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Start near the sensor and walk
away at a constant slow speed
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time (sec)
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time (sec)
Start near the sensor and walk away
speeding up
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time (sec)
time (sec)
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Start near the sensor and walk away
slowing down
Start away from the sensor and walk
near speeding up
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Start away from the sensor and
walk near slowing down
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time (sec)
time (sec)
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. Use a ruler when making straight lines.
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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Time
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Time
Procedure D: Graph of nonconstant 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
3
3
8
4
14
5
22
6
32
7
44
2. 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?