Lab 6; Friction (Report on Part 3 & 4 for Sandpaper)

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University of Southern Mississippi *

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111L

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Mechanical Engineering

Date

Dec 6, 2023

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docx

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17

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Lab 02: “Friction”; Part 3 and 4 for Sandpaper Date Performed: Oct 21, 2023 Date Submitted: Oct 24, 2023 Student: Kyra Pell (Ann) USM ID: w10132479 TA: Shwe Oo
Purpose Friction is defined as the force resisting the relative motion of objects sliding against each other, whether they be solid surfaces, fluid layers, or material elements. The purpose of this experiment was to determine the forces and coefficients of static and kinetic friction of a sandpaper friction block against a wooden board, as well as calculate the maximum angle of repose of the sandpaper block. The measured physical quantities of this experiment are the mass of the block (g), the kinetic frictional forces F k (N), the static frictional forces F s (N) and finally the angles at which the sandpaper friction block starts to slide down a wooded board. The physical quantities that are calculated are the total weight of the block and hanging weight (N) (also known as the normal force), the average static and kinetic frictional forces of three trials, their corresponding coefficients ( μ s ) and ( μ k ), the maximum angle of repose, the average angle of repose regarding three trials, and finally, the precent difference (%) of said angle. The physical principles used during this experiment are the properties of friction and frictional forces. Introduction As previously stated, the purpose of this experiment was to determine the forces and coefficients of static and kinetic friction of a sandpaper friction block and its maximum angle of repose. To do this I first needed to measure the mass (g) of the sandpaper friction block, add the mass of a 100 (g) hanging weight, then convert the total to kilograms (see equation 1) and calculate its weight (see equation 2). I then set the sandpaper block flat on a wooden board. After this, I set the 100 (g) hanging weight in the center of the block and connected the block to a spring scale set at zero. I then measured, in newtons, the kinetic friction force and the static friction force three times each. After words I took these values and then proceeded to calculate the corresponding avg forces (see equation 3). Using these values, I then calculated the correlating coefficients (see equations 4 & 5). Then using the static friction coefficient, I calculated the maximum angle of repose for the sandpaper friction block (see equation 6). Then after removing the weight, and placing the block in the same starting position, I lifted the wooden board until the friction block just started to slide, and measured the angle using a protractor, a string, and a small hanging weight. I repeated this step three times. Using these measured angles, I then calculated the avg angle of repose (see equation 3). Finally, I calculated the percent difference between the predicted maximum angle of repose and the average measured maximum angle (see equation 7). The physical assumptions of this experiment are that I made accurate measurements with my scale, and protractor. Also, that I made accurate calculations. Equation 5 Equation 6 Equation 1 Equation 2 Equation 4 Equation 7 Equation 3
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 Data, Calculations, and Questions 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.
Categorize each statement as True or False. True False 1 2 Static friction is caused by molecular Kinetic friction is caused by molecular bonds. bonds. Friction between objects increases Friction does not always increase the thermal energy of both objects. temperature of interacting objects. Increasing in the normal force between Increasing the surface area of two objects increases the friction force interaction between two objects between them. increases the friction force between them. Exploration The force of friction always acts parallel to the surface of interaction. True False When the objects are moving relative to one another, the speed of the moving object affects the magnitude of what is known as the kinetic friction force. True False The force of static friction is always equal to the coefficient of static friction multiplied by the normal force. True False
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 ma x 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 F N F N μ k = z app μ k = F app × F N None of the above
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