Download Friction Lab

Name: ____________
Why do people
always ignore me?
Mr. Friction
Objective:
Determine how an object’s mass affects the friction it experiences.
Determine the coefficients of static friction for two different friction materials and compare
those coefficients to determine which material has more friction.
Determine the coefficients of kinetic friction for two different friction block materials and
compare those coefficients to determine which material has more friction.
Compare the coefficient of static friction to the coefficient of kinetic friction for each
friction block material to determine whether it is easier to make an object start to move or
to keep a moving object in motion at a constant velocity.
Safety: Be sure your car drives toward the end of the track with the stopping bracket.
Materials:
Obtain a handy PASCO set up including…
 A track!
 A felt or cork or plastic friction block!
 A force sensor (with hook attachment ) and USB link!
 A self-propelled PASCAR
 Some string!
Procedure:
1. Pick one of the friction blocks. Tie a small piece of string through the hole on the end of the
friction block.
2. Plug in that force sensor!
3. Launch Data Studio and click on “Setup” in the top right. Uncheck “push positive” and check
“pull positive.” On the graph, hover over the axis title on the y-axis until you see a little ladderlike symbol. Right click and select “pull positive.”
4. Now double-click the words “Force, pull positive” near the upper left of your screen. Change
the precision to 3.
5. Attach the force sensor to the back of the PASCAR so that the sensor’s hook is in line
horizontally with the friction block string. Loop the friction block’s string through the force
sensor’s hook.
6. Click “Start” on the computer. With slack in the string, press the “zero” button on the sensor.
7. Reread the safety for this lab. Then turn on the car and allow it to pull the block down the
track. Stop the car before it gets to the end of the track.
8. Click the “Stop” button after pulling the block from one end of the track to the other.
9. Look at your graph. After an initial spike, the graph should be fairly flat. If it is, proceed to step
eleven. If it’s not, proceed to step ten.
10. You stink at this game. (Kidding! ) Erase your last data run and then go back to step six.
11. Do not erase your data. Take a second data run, but this time put a 0.250kg mass in the
friction tray. Repeat steps six through nine.
12. Dude, repeat step eleven. (This means you’re taking a third data run with 0.500kg in it.)
13. Mass your friction tray. Record the data and do some handy calculations in order to fill out
the first three columns under Table 1 of “Our Data Wonderland” at the end of this packet.
14. On your graph Frictional Forces vs. Time graph, select the first data run (from the empty
block.) Use the Smart Tool to find the maximum friction force at the highest point of the first
spike. In other words:
right
thar
Let’s call this value the maximum static friction! (Won’t that be fun?)
15. Enter this force in the appropriate spot in Table 1.
16. Repeat steps fourteen and fifteen for the other two data runs.
17. Fill in the column in Table 1 labeled “Maximum Static Friction ÷ Normal Force” by doing the
appropriate calculations.
18. On your graph Frictional Forces vs. Time graph, select the first data run again (the run with
the empty friction block.) Highlight the flat portion of the graph after the initial spike.
right
thar
19. Now you need to record the mean (average) of that highlighted portion. If the computer isn’t
showing the mean of the highlighted portion, click the  button. Enter the mean force for this in
the appropriate spot in Table 3. Let’s call this value the average kinetic friction! (Won’t that be
fun?)
20. Repeat step nineteen for the other two data runs.
21. Fill in the column in Table 3 labeled “Maximum Static Friction ÷ Normal Force” by doing the
appropriate calculations. (The normal forces, in case you’ve forgotten, are in Table 1.) 
22. Take a screen shot of your graph and save it somewhere that your lab team can access
later.
23. Now clear all of the data runs, exchange your friction block for one other type and repeat
steps 6 – 22, remarking all the while about how much you love physics. 
NOTE: These data tables are similar to but not identical to the ones you will include in your lab
report. They are only included here to help you organize your information while doing the lab.
Table 1 – Maximum Static Friction of
Mass
(kg)
Weight
(N)
Normal
Force
(N)
(Write in the material)
Maximum
Static
Friction (N)
Coefficient of
Static Friction
(Maximum Static
Friction ÷
Normal Force)
Empty
tray
Tray +
0.250kg
Tray +
0.500kg
Table 2 – Maximum Static Friction of
Mass
(kg)
Weight
(N)
Normal
Force
(N)
(Write in the material)
Maximum
Static
Friction (N)
Coefficient of
Static Friction
(Maximum Static
Friction ÷
Normal Force)
Empty
tray
Tray +
0.250kg
Tray +
0.500kg
Table 3 – Kinetic Friction of...
Average
Kinetic
Friction (N)
Table 4 – Kinetic Friction of...
Coefficient of
Kinetic Friction
(Average
Kinetic Friction
÷ Normal
Force)
Average
Kinetic
Friction (N)
Empty
tray
Empty
tray
Tray +
0.250kg
Tray +
0.250kg
Tray +
0.500kg
Tray +
0.500kg
Coefficient of
Kinetic Friction
(Average Kinetic
Friction ÷
Normal Force)
Data Tables & Graphs:
In a spreadsheet, create the following data tables:
A table showing the maximum static friction and the coefficient of static friction for
the first block with the three different masses. This table should also show the
average coefficient of static friction for these three runs.
A table showing the maximum static friction and the coefficient of static friction for
the second block with the three different masses. This table should also show the
average coefficient of static friction for these three runs.
A table showing the average kinetic friction and the coefficient of kinetic friction
for the first block with the three different masses. This table should also show the
average coefficient of kinetic friction for these three runs.
A table showing the average kinetic friction and the coefficient of kinetic friction
for the second block with the three different masses. This table should also show
the average coefficient of kinetic friction for these three runs.
Also include a screen shot of the three data runs for ONE of your friction block
materials.
Data Analysis:
Your teacher will provide you with the actual coefficients of friction. Please do four
percent error calculations:
Percent error for the average coefficient of static friction for the first block
Percent error for the average coefficient of static friction for the second block
Percent error for the average coefficient of kinetic friction for the first block
Percent error for the average coefficient of kinetic friction for the second block
Conclusion: Be sure to address each of the four objectives. You should also give a
statement what your results say in general about the two types of friction and their effect
on motion.
Comments: Be sure to write two academic comments.
I love
her…
I love
physics!