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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!