Sheridan College
Faculty of Applied Science and Technology (FAST)
APPLIED MECHANICS 2 – ENGI 13386(FALL 2014)
Lab Report 3
Pulley Friction
Class: 1149_40517 (Group Number: 6)
Authors: Paritosh Chahal, Sandeep Sidhu, and Rony George
Date of Experiment: 8th October 2014
28 October 2014 – 6 pm Instructor M. Arthur
Signed Declaration: the work submitted here is my own and not copied or plagiarized from another source.
Table of Contents
Executive Summary: 3
Objectives: 3
Theory: 3
Equipment and Material used: 4
Procedures: 5
Data: 5
Sample Calculations: 6
Results: 9
Discussions: 11
Conclusion: 12
Real life application: 13
Contribution Table: 14
References: 14
Appendix: 15
Executive Summary:
Friction is defined as a force “parallel to a flat surface or tangent to a curved surface” (Walker 233) and “opposite in direction to the motion impending motion" (Walker 233). Friction force is really useful in the society since it helps generate heat, operate breaks in transportation systems, and operate assembly lines and machine parts with v-belt lines and v-belt pulleys properly. Even though friction itself is a blessing, it still has some disadvantages like objects wear out after long time of use, and affect tool/machine lives (machines parts which have reduce live due to friction can break down the machine which later will affect company’s production efficiency and profits).
As mentioned earlier, many machine parts like v-belt drives, v-shaped pulleys, and flat shaped pulleys needs friction for running the machine properly. The purpose of this lab is to find the coefficient of friction at three different angles of the cotton rope and metal pulley. After following the producer of the lab, and performing the lab. The data was collected which showed that as the angle of contacts was increased, the ratio of decreases (Note: the mass from the Data table is converted to tension force by multiplying each weight by 9.8 m/s2). After collecting the data calculations were performed to find the coefficient of friction between the rope and the pulley; it was concluded that the coefficient of friction between the rope and pulley was 0.2785 which would have been affected by errors which will be later discussed in this lab.
Objectives:
The objective of this lab was:
a. Find the coefficient of friction at three different contact angles.
b. To check the ratio of at different contact angles
Theory:
As mentioned in before, friction force is a force that acts against impending motion and requires two surfaces in contact. These forces occur in linear motion (box pushed on a slope or straight surface) and rotation motion (belt friction). For rotational motion friction, one need has to make two assumptions:
a. A rope, flat belt, or cable is used which is attached to a pulley.
b. There is impending motion. (In a moving pulley, the TL will be against the motion. While for a fixed pulley, the TL will be with the motion).
When a rope is placed on a pulley to do work, the “rope will have two different tensions, a large tension (TL) and a small tension (Ts)” (Walker 244) {Fig 1}. The two forces (during impending motion) depend on angle of contact at the pulley, and the coefficient of friction. Combing the three together will give us the formula:
Figure 1: Pulley system with TL and TS
NOTE: The above formula can only be used for simple pulleys, for V-shaped pulleys {Figure 2}, we use a different formula {Figure 3}.
Equipment and Material used:
a. Pulley system {Figure 4}: The pulley system is used find the coefficient of friction between the rope and pulley wheel by putting weights at each end of the rope (one has to first insert the mass which denotes Ts. To find the TL, one has to keep on adding weights on the other end until the TL side moves down a bit).
b. Weights: Used to create a tension (by inserting it on
