Static and Kinetic Friction Lab Report

07/04/2020 Static and Kinetic Friction Lab Report Introduction and Abstract: If you slide one object over the surface of another object, there will be a force opposing that motion. This resistance force is called friction and this force is parallel to surfaces. Friction is one of two contact forces, the other being normal force. There are many types of frictional forces, but the two most common types are static friction and kinetic friction. Static friction exists between surfaces at rest and kinetic friction exists between sliding surfaces or surfaces in motion. One method of evaluating frictional forces, defining the coefficient of friction, is found by the ratio of frictional force over normal force. This report explores and analyzes these frictional forces within different materials. The objective of these experiments is to determine if the coefficient of friction changes with load, and compare the coefficient of friction for various materials. Our goal is to determine the relationship between loads and frictional forces, determine the effects of surface area, and compare the effects of different materials. Procedures: For part A of the experiment, we will find the coefficient of static friction by raising a wooden plank to determine the angle at which the object begins to slide . For glass, Ceramic / Stone, RubberAcrylic, Brass, Steel, Copper, Nylon, and PVC cubes, we will Measure the coefficient of static friction for the wood block on the wood plank and Calculate the normal force, the force of static friction, and the coefficient of static friction for the average maximum angle of repose. For part B of the experiment, we will find the coefficient of kinetic friction for the wood on wood interface by applying various loads and determining how much force is required to bring the system to a state of constant velocity. We will measure the kinetic friction force for six different loads on the block, calculate the normal force, the force of kinetic friction, and the coefficient of kinetic friction for each load. For part C we will do the same process as stated in part B, exceptthe block will be on its narrow side to create data for a comparison of friction and surface area. 07/04/2020 Data Tables, Calculations, and Analysis: Data Table for Part A – Static Friction On An Inclined Plane Material Trial 1 θ deg Trial 2 θ deg Trial 3 θ deg Trial 4 θ deg Trial 5 θ deg Average Angle θ ave deg Std. Dev. Angle σ θ deg Block 16.6 16.8 16.3 16.3 16 16.4 .308 Glass 18.9 19.1 19.2 18.8 20 19.2 .474 Ceramic 17.5 17.3 17.4 17.9 17.1 17.44 .297 Rubber 21.6 21.6 21.5 21.6 21.5 21.56 .055 Aluminum 17.4 17.6 17.5 17.5 17.8 17.56 .152 Brass 18 17.9 18 17.5 18 17.88 .217 Steel 19.4 20 19.6 19.6 19.5 19.62 .228 Copper 18.1 18 18 20 17.9 18.4 .897 Nylon 21.1 21 22 21.5 21.8 21.48 .432 PVC 18.3 19 18.4 18.3 18.4 18.48 .295 Material Mass m kg Normal Force F N N Force of static friction F s N Coefficient of static Friction μ s Error in Static Friction δ μs Block .12573 1.18 .348 .294 .047 Glass .05447 .505 .176 .348 .007 Ceramic .03143 .294 .092 .314 .027 Rubber .03798 .347 .137 .395 .054 Aluminum .04224 .395 .125 .316 .025 Brass .1344 1.25 .405 .323 .018 Steel .12719 1.18 .419 .356 .015 Copper .14379 1.34 .445 .333 .008 Nylon .02249 .205 .081 .394 .053 PVC .01819 .169 .057 .334 .007 07/04/2020 Data Table for Part B – Kinetic Friction for Wood on Wood Mass of Block m B = .12573 kg Mass of Hangar m H = .0100 k g Load mass m 1 (kg) Control Mass m c (kg) Normal Force F N (N) Force of kinetic Friction F K (N) Coefficient of Kinetic Friction μ k 0 .20 1.23 .294 .239 .100 .035 2.21 .441 .200 .200 .060 3.20 .687 .215 .300 .075 4.18 .834 .200 .400 .090 5.16 .981 .190 .500 .115 6.14 1.23 .200 Average .207 St. dev. .017 % Difference 34.7% 07/04/2020 Data Table for Part C – Kinetic Friction and Surface Area Mass of Block m B = .12573 kg Mass of Hangar m H = .0100 kg Load mass m 1 (kg) Control Mass m c (kg) Normal Force F N (N) Force of kinetic Friction F K (N) Coefficient of Kinetic Friction μ k 0 .020 1.23 .294 .239 .100 .035 2.21 .441 .200 .200 .065 3.20 .736 .230 .300 .075 4.18 .834 .200 .400 .095 5.16 1.03 .200 .500 .110 6.14 1.18 .192 Average .210 St. dev. .019 % Difference 33.3% Part B %Difference 1.44% 07/04/2020 Conclusion: In these experiments, we explored how different factors impact the frictional coefficient of an object. In experiment A, we performed a simple run where we record the maximum angle needed to displace a material from its resting position. The data shows that different materials do impact the frictional coefficient of an object. The texture of the surfaces of objects may allow for more resistance than others. For experiment B, we varied the load carried by a wooden block sliding across a wooden surface on a pulley system. The trend in our data supports the idea that friction increases with load carried. Our graph’s trendline with a slope of .188 has a 9.6% difference from our friction coefficient of .207 in part B. In the pre-lab I predicted the y intercept to be 0, and the y-intercept is .0531, which means that frictional forces will exist even when normal force is at equilibrium (0). In experiment C, performed the same procedures as part B, but used the narrow side of the block. According to the data gathered in our experiment, surface area does not have a significant impact on the frictional coefficient. There is only a 1.44% difference from our data in part B. Overall we were able to conclude that different textures exert different frictional forces, surface area has an insignificant impact on frictional forces, and the frictional coefficient is proportional to load of an object.