Physics111L_Friction_291291

A force that acts parallel to the surface 1 Friction A force that acts perpendicular to the surface 2 Normal A force that increases as applied force increases up to some maximum value 3 Static friction Magnitude depends on the interacting materials 4 Coefficient of friction A force that is constant regardless of the applied force 5 Kinetic friction Physics 111L Friction Final Report Student Name Kyra Pell Student ID 291291 Lesson Friction Institution University of Southern Mississippi Session Fall 2023 Course Physics 111L Instructor Sidney Gautrau Test Your Knowledge Match each term to the best description.

1 N 2 f 4 mg sinθ 3 mg cosθ 1 2 4 3 Static friction μ k Kinetic friction μ s Label the force arrows on the free-body diagram. Label the force versus time graph.

The force of kinetic friction for a particular pair of interacting objects is always the force of static friction. less than greater than equal to None of the above Static friction is caused by molecular and kinetic friction is caused by molecular . attraction; bonds attraction; repulsion bonds; attraction None of the above The coefficient of static friction is related to the maximum angle of repose by . μ s = sin θ max μ s = tan θ max μ s = θ max None of the above The coefficient of kinetic friction is found from the equation: . μ k = F app FN F N μ k = F app μ k = F app × F N None of the above

rce up to some maximum value. With this said, once an object starts to slide along the surface of another object, the friction force between the objects b e nature of the interaction), the normal force (which is related to the weight of the object and the angle of the surface) and the properties of the surfaces orce needed to move the block in either position is the same as well. Since we know that surface area has no direct effect on the forces of friction, this le e greater the static force needed to indicate movement. This in turn, effects the static friction coefficient, meaning that the less surface area between the The force of friction is always represented as a horizontal arrow in a free- body diagram. True False Exercise 1 Explain the difference between static friction and kinetic friction. Discuss the relationship between friction, normal force, and surface area. Compare the static and kinetic friction forces and coefficients determined for the flat wooden friction block and the wooden friction block on its side that were recorded in Data Table 1. What was the relationship of surface area to the force and coefficient of friction between the objects?

her surface than all of the materials leading to the highest coefficients. Note that smooth surfaces tend to have fewer points of contact on a molecular level than rough surfaces. Molecular bonds form where the surfaces do to happens with a constant velocity. During the scenario the kinetic frictional force can be directly measured under the conditions where it is in equilibrium se, it is necessary to measure the applied force just before the block begins to move. This allows us to determine the maximum force of static friction tha tion opposes motion and manifests in various ways, such as static friction that keeps an object at rest, kinetic friction that acts on moving objects, rolling Which material among the four you tested has the largest coefficients of static and kinetic friction? Which material has the smallest? Does this make sense? Why or why not? When attempting to determine the coefficient of kinetic friction, why is it necessary to move the block with constant velocity? When attempting to determine the coefficient of static friction, why is it necessary to measure the applied force just before the block moves? Are these two scenarios (constant velocity and almost in motion) the only scenarios when friction is present? Explain your answer.

Data Table 1: Friction and Surface Area Mass (g) Weight (N) F k Trial 1(N) F k Trial 2 (N) F k Trial 3 (N) Average F k (N) μ k Flat 5.18 1.40 1.30 1.35 1.35 0.26 Side 5.18 1.30 1.40 1.35 1.35 0.26 Weight (N) F s Trial 1(N) F s Trial 2(N) F s Trial 3(N) Average Fs (N) μ s Flat 5.18 1.90 1.80 1.85 1.85 0.36 Side 5.18 2.00 2.10 2.00 2.03 0.39 Data Table 2: Friction and Normal Force Weight (N) F k Trial 1 (N) F k Trial 2 (N) F k Trial 3 (N) Average F k (N) μ k calc. μ k calc. avg. μ k graph 5.18 1.40 1.30 1.35 1.35 0.26 0.24 0.28 1.26 0.30 0.35 0.30 0.32 0.25 0.77 0.20 0.15 0.15 0.17 0.22 Weight (N) F s Trial 1 (N) F s Trial 2 (N) F s Trial 3 (N) Average F s (N) μ s calc. μ s calc. avg. μ s graph 5.18 1.90 1.80 1.85 1.85 0.36 0.36 0.36 1.26 0.50 0.40 0.50 0.47 0.37 0.77 0.30 0.25 0.25 0.27 0.35 Graph 1: Static Friction 28.6

Data Table 4: Maximum Angle of Repose Competency Review The friction force is proportional to the normal force on an object. inversely directly quadratically None of the above The influences the magnitude of the static friction force. normal force coefficient of static friction applied force All of the above Material Weight (N) F k Trial 1 (N) F k Trial 2 (N) F k Trial 3 (N) Average F k (N) μ k Wood 1.26 0.30 0.35 0.30 0.32 0.25 Glass 1.53 0.15 0.15 0.10 0.13 0.08 Sandpaper 1.53 0.70 0.75 0.70 0.72 0.47 Paper 1.27 0.30 0.25 0.30 0.28 0.22 Weight (N) F s Trial 1 (N) F s Trial 2 (N) F s Trial 3 (N) Average F s (N) μ s Wood 1.26 0.50 0.40 0.50 0.47 0.37 Glass 1.53 0.25 0.20 0.20 0.22 0.14 Sandpaper 1.53 0.90 0.80 0.85 0.85 0.56 Paper 1.27 0.50 0.50 0.55 0.52 0.41 material θ (°) calc. θ (°) Trial 1 θ (°) Trial 2 θ (°) Trial 3 θ (°) Average % Difference Wood 20.3 30.0 27.0 29.0 28.7 8.6 Glass 8.0 13.0 15.0 13.0 13.7 13.1 Sandpaper 29.2 30.0 30.0 34.0 31.3 1.7 Paper 22.3 25.0 26.0 24.0 25.0 2.9

The coefficient of static friction for a certain pair of materials is greater than the coefficient of kinetic friction for the same pair of materials. True False Smooth surfaces have more points of contact on a molecular level than rough surfaces. True False The friction force as represented in a free-body diagram always has the same length as the applied force. True False A box of tools rests in the back of a pickup truck. The truck accelerates to the north and the box remains at rest in the truck. The direction of the friction force on the box of tools is . north south zero None of the Above A block of mass 10 kg rests on an incline of 20°. The magnitude of the friction force on the block is N. 98 92 34 None of the above