lab106(2) - 1 Lab 106(2 Static and Kinetic Frictions 2...

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1. Lab 106(2): Static and Kinetic Frictions2. IntroductionWhenever the surface of one object slides over another surface, friction results. The frictional force is always parallel to the action of these surfaces, opposite of the motion relative to the other. Suppose a system exists where a block is at rest on a table. An applied force is created. Static frictional force (fs), increases, balancing out the applied force until the object starts sliding. At the moment right before the object starts sliding, the maximum fs was reached. The relationship between the fsmaxand the normal force, FN, is as followed: fsmax= μsFN.Once an object begins sliding, kinetic friction takes over static friction. The kinetic, or sliding friction between two surfaces is given by: fk= μkFN. If sliding takes place at a constant speed, Newton’s First Law applies to the system. The coefficient of kinetic friction is always smaller than the coefficient of static friction. It requires a greater force to start an object moving than it takes to maintain movement.3. Experimental ProcedurePart I. Find Static and Kinetic Friction Coefficients between wooden cart and friction apparatus under a horizontal condition.1. The USB cable of the 850 Universal Interface was connected to a USB port on the computer. 2. The AC adapter power cord was connected to an electrical outlet under the lab table.3. The computer program to be used for the lab was opened up. 4. The mass of the wooden cart was measured to be 85.09 grams or 0.08509 kg. 5. The force sensor was zeroed.6. The wooden cart was put on the friction apparatus. The top of the pulley was observed to be the same height as the hook of the cart, threaded over a wheel and onto the table.7. The record button in the program was pressed.8. The motion sensor was slowly pulled until the cart started to move. We then continued to pull the cart at constant velocity. 9. After obtaining data, we pressed the stop button and clicked to the Analysis 1 page. 10. Data was selected for use using the select visible data tool. Looking at the generated chart, we approximated for coefficients of kinetic and static friction.
11. We clicked to the page Analysis 2 and entered the coefficients found in step 10 along with thecalculated normal force for each trial. 12. Steps 5-11 were repeated for 5 trials, with 5 different normal forces for the friction tray.13. In the page Analysis 2, there were data points formed on a Ffv. FNgraph for every trial. Two points were generated for each trial, one point for the kinetic friction, and one point for the static friction. At the end of 5 trials, lines of fit were generated with the curve fit tool for the points of static friction and kinetic friction separately. Part II. Wooden Cart Moving Up and Inclined Plane1. The critical angle (15.6o) for the wooden cart to be on the verge of sliding down an inclined plane was experimentally determined.

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