Lab 1A 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 distance vs. time graph for constant velocity would look like.
Include your reasoning.
Vocabulary: speed
Materials:
velocity
constant velocity buggy
meter stick
Laptop computer or phone with metronome app
Laptop computer with motion detector
Procedure A: Constant velocity buggy
1. Tape 5 meters of adding machine tape on the floor.
2. Draw a start line on the paper.
3. Find a free metronome app for your phone or a free website on the lab top, for
instance http://www.webmetronome.com/. You will want to set it for 60 beats per
minute or possibly 30 beats per minute.
4. THIS MAY TAKE MUCH PRACTICE TO GET IT RIGHT. DO NOT KEEP ANY
OF THE DATA UNTIL YOU ARE COLLECTING DATA CORRECTLY!
Start the metronome, start the buggy, set the front tires of the buggy at the start line
on a beat and make a dot on the paper with a marker where the front tires are at each
beat, for at least 10 dots. 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.
5. Repeat this procedure with the other buggy so you have two sets of data. Use a
different color marker for this set of dots. Keep the tape for Procedure B.
Analysis A: Constant velocity buggy
1. Measure the distance from the start line to each dot for the first 10 dots.
2. Graph the data for both buggies on one graph.
3. Calculate the slope and y-intercept for each line. Write the equation of the line for
each line graphed.
Procedure B: Constant velocity buggy with different starts
1. Choose one buggy to use for this whole procedure.
2. Tape down a new 5 meter piece of paper (flip the paper to use other side) and draw a
zero line that is 20 cm from the end of the tape and label it. Draw another line 10 cm
before the zero line (10 cm from end of tape) and label it “start line”.
3. Run the experiment the same way as above except start with the buggy 10 cm before
the start line. Measure the distances from the start line to each dot for the first 10
dots.
4. Take the batteries out and switch them around. This should cause the buggy to run
backwards (if it doesn’t then you will need to just run it forwards pointed towards the
start line). Perform the experiment again this time with the buggy at the opposite end
of the tape and have it move towards the start line. Make a start line at the opposite
end of zero and have the buggy move towards zero. Use a different color marker.
Measure the distances from the dot to the zero line (make sure you start at first dot
you made).
Analysis B: Constant velocity buggy with different starts
1. Graph the data for both buggies on one graph.
2. Calculate the slope and y-intercept for each line. Write the equation of the line for
each line graphed.
Conclusion A & B:
1. What does the slope of the line tell about each buggy? What does the y-intercept tell
about each buggy? Be as specific as possible.
2. Compare the two slopes & y-intercepts for procedure A. Compare the two slopes &
y-intercepts for procedure B.
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.
2. Position the sonic ranger on a lab station so that its beam is about chest high and
aimed horizontally.
3. Open the folder “Physical Science with Vernier”. Open the file “35a Graphing You
Motion”. 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.
4. 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. Is the graph linear or a curve (ignore the little bumps & wiggles).
5. Record a sketch of the graph in your lab book (include a description of how you
walked). Use a ruler and number and title each graph.
6. Make sure each person in the group understands this graph before moving on to the
next graph.
7. Perform procedure for all 8 graphs.
Start away from the sensor and walk
near at a constant slow speed
Stand still
d
i
s
t
a
n
c
e
d
i
s
t
a
n
c
e
m
m
time (sec)
time (sec)
Start near the sensor and walk
away at a constant fast speed
d
i
s
t
a
n
c
e
Start near the sensor and walk
away at a constant slow speed
d
i
s
t
a
n
c
e
m
m
time (sec)
d
i
s
t
a
n
c
e
time (sec)
Start near the sensor and walk away
speeding up
d
i
s
t
a
n
c
e
m
m
time (sec)
time (sec)
d
i
s
t
a
n
c
e
Start near the sensor and walk away
slowing down
Start away from the sensor and walk
near speeding up
d
i
s
t
a
n
c
e
Start away from the sensor and
walk near slowing down
m
m
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.
d
i
s
t
a
n
c
e
d
i
s
t
a
n
c
e
Time
d
i
s
t
a
n
c
e
Time
Time
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
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?