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Transcript
```Name: ____________
Date: _______________
Period: ______________
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.
Determine the coefficients of kinetic friction for two different friction block materials and
compare those coefficients.
Compare the coefficient of static friction to the coefficient of kinetic friction for each
friction block material.
Determine whether it is easier to make an object start to move or to keep a moving object
in motion at a constant velocity. Justify this conclusion with data.
Safety: Behave with basic lab safety.
Materials:
Obtain a handy PASCO set up including…
 A track!
 A cork or felt friction block!
 A force sensor with USB link!
 Some string!
Procedure:
1. Pick either a cork or felt friction block. Tie a small piece of string to connect the hook on the
force sensor to the friction block.
2. Plug in that force sensor!
3. Select “08 Friction Forces CF.ds.”
4. Can you see the graph labeled Friction Forces vs. Time? If yes, go on to step six. If no,
continue with step five.
5. Call your teacher over for help.
6. Hold the force sensor horizontally a few inches above the track. With slack in the string, press
the “zero” button on the sensor.
Why do people
always ignore me?
Mr. Friction
7. Click the “Start” button and gradually pull on the sensor with an increasing force. Once the
block starts moving, it is very important to pull so the block moves with a constant velocity.
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. 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 250-gram mass bar on
the friction tray. Repeat steps six through nine.
12. Dude, repeat step eleven. (This means you’re taking a third data run with 500 grams on 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 (felt) OR Table 2 (cork) 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 (felt) OR Table 2 (cork.)
16. Repeat steps fourteen and fifteen for the other two data runs.
17. Fill in the column in Table 1 (felt) OR Table 2 (cork) 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 (felt) OR Table 4 (cork.) 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 (felt) OR Table 4 (cork) labeled “Maximum Static Friction ÷
Normal Force” by doing the appropriate calculations. (The normal forces, in case you’ve
forgotten, are in Table 1 (felt) or Table 2 (cork.)) 
22. Now clear all of the data runs, exchange your friction block for the other type (felt or cork,)
and repeat steps 6 – 21, 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
Table 1 – Felt: Maximum Static Friction
Mass
(kg)
Weight
(N)
Normal
Force
(N)
Maximum
Static
Friction (N)
Coefficient of
Static Friction
(Maximum Static
Friction ÷ Normal
Force)
Empty
tray
Tray +
250g
Tray +
500g
Table 2 – Cork: Maximum Static Friction
Mass
(kg)
Weight
(N)
Normal
Force
(N)
Maximum
Static
Friction (N)
Coefficient of
Static Friction
(Maximum Static
Friction ÷ Normal
Force)
Empty
tray
Tray +
250g
Tray +
500g
Table 3 – Felt: Kinetic Friction
Average
Kinetic
Friction (N)
Table 4 – Cork: Kinetic Friction
Coefficient of
Kinetic Friction
(Average
Kinetic Friction
÷ Normal
Force)
Average
Kinetic
Friction (N)
Empty
tray
Empty
tray
Tray +
250g
Tray +
250g
Tray +
500g
Tray +
500g
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 felt 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 cork 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 felt 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 cork block with the three different masses. This table should also show
the average coefficient of kinetic friction for these three runs.
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 felt block
Percent error for the average coefficient of static friction for the cork block
Percent error for the average coefficient of kinetic friction for the felt block
Percent error for the average coefficient of kinetic friction for the cork block
Conclusion: Be sure to address each of the five objectives.