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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 report. They are only included here to help you organize your information while doing the 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. Comments: Be sure to write two academic comments. I love her… I love physics!