PH-11 lab 2

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Mechanical Engineering

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Feb 20, 2024

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Unit 1 Kinematics October 27, 2021 Lab 2.1: Force of Friction Purpose: - To find the coefficient of dynamic friction between 2 surfaces. Procedure: - A spring balance was used to measure the force of gravity of 5 nearly same blocks of wood and the values were then written on the blocks. - The spring balance was then adjusted so it read 0 when horizontal then it was attached to the hook on one of the blocks which was placed on the Tabletop. - The smallest force is required to move the block at a slow, steady speed along the tabletop. The table was measured. Several trials took place, and the average was calculated for the force of sliding friction. - The steps above were repeated by placing a second, third, fourth, and fifth block on top of the first one. Results/analysis: Observation: N/A Data table for Force of Friction vs. Force of Gravity: Number of blocks Total force of gravity,F g (N ± ?N) Force of friction, F f (N ± ?N) 1 2.2 ± 0.1N 0.8 ± 0.1N 2 4.8 ± 0.2N 1.2 ± 0.1N 3 7.6 ± 0.3N 2.3 ± 0.1N 4 10.3 ± 0.4N 3.3 ± 0.1N 5 13.1 ± 0.5N 3.8 ± 0.1N Graph: The graph is attached to the lab. Calculations:

Added mass of blocks 1 and 2 plus uncertainty to find Fg of block 2. →2.2±0.1 N + 2.6±0.1N=4.8±0.2N Slope: = =0.25625 → 0.26 𝑅𝑖𝑠? 𝑅𝑢𝑛 ?2−?2 ?2−?1 = 𝐹?2 − 𝐹?1 𝐹?2 − 𝐹?1 = 3.51𝑁−3.1𝑁 12.0𝑁−10.4𝑁 Average for Fn: Calculated the average of block 1. First trail Second trail Third trail Average 0.7N 0.8N 0.8N 0.8N±0.1N (0.7N+0.8N+0.8N) 3= 0.8N ÷ Calculations for the uncertainty is the largest difference between the average and the volumes measured, in this case±0.1N. Questions: 1. What happened to the force of friction as you added the blocks together? The force of friction increases when the number of blocks increases. 2. Explain the reasoning that allowed you to determine that the force used to pull the blocks at a constant speed is equal to the force of friction? It is because it is moving in a straight line at a constant speed. One other reason is that the acceleration was zero therefore the net was zero. This makes the force of friction applied equal to the force. 3. Name three situations in which you need to have a) A low coefficient of friction Three situations in which you need to have a low coefficient of friction are, skating on ice, socks on a wooden floor, and snowboarding on snow. b) a high coefficient of friction Three situations in which you need to have a high coefficient of friction are Brakes on a car, Sanding wood with sandpaper, and Rubber tires of a car on the road.

Discussion: Source of error: ● The first source of error was the surface of the table where the blocks were moving. The surface on the tables, the blocks were measured, had bumps and some of the places were painted therefore made the frictions different in some areas than other areas. One way to reduce the sources of error was to change the table/setting when the blocks were getting dragged at a constant speed. ● The second source of error was that it was not possible to move the blocks at a constant speed. The experiment wanted the individual to move the blocks at a constant speed but it is not possible because of human reflexes/human problems. This error affected the measurements. There was no other way to reduce the error in this lab unless the instructions were different. Conclusion: The purpose of this lab was to find the coefficient of dynamic friction between two surfaces which was 0.26.

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