MECE 102 Engineering Mechanics Lab A First Year

MECE 102: Engineering Mechanics Lab A First Year Course in Newtonian Mechanics, Experimentation, and Computer Tools Created by the Faculty of the Mechanical Engineering Department in the Kate Gleason College of Engineering at RIT

Week 4 Lecture Newton’s 3 rd Law • We will study the motion of two bodies constrained by a cable moving under the influence of Newton’s Laws. • We will again be using the Ultrasonic Transducer. • The acceleration of each body will be compared to the local acceleration of gravity.

The week 4 Lab experiment comprehends two moving masses that are “kinematically constrained”. Describe how the “kinematically constrained” scenario is implemented in the context of our Week 4 Lab Experiment.

FACET Problem Solving Method Recall from Recitation and Ch. 1. 4. 2 the problem solving method we will be using in class: • Formulate • Assume • Chart • Execute • Test • Iterate

FORMULATE: State the Known Information • A system consists of two masses, m 1 and m 2, and an ideal pulley, P. The masses m 1 , m 2 , and pulley P interact by means of an ideal cable. • The first mass m 1 is positioned on a rough-surface ramp inclined at an angle to the horizontal. The ideal cable connects from mass m 1 over the ideal (frictionless) pulley P to m 2. • The second mass m 2 is suspended from the ideal cable. The ideal cable is of a constant length. • The system is released from rest and allowed to move due to the action of gravity, g.

FORMULATE: Identify Assumptions Clearly identify and justify all Assumptions used in analysis:

CLICKER: When analyzing the system in Week 4 we assume that the Pulley is an ideal Pulley. What does the term “ideal” mean in this context? • Select your Answer: A. B. C. D. Massless Frictionless Both A) and B) None of the above

CHART: Schematic Diagram Figure 4. 1: Schematic Diagram of two bodies in relative motion.

CHART: Free Body Diagrams Figure 4. 2: Free Body Diagrams for a pulley assembly and two bodies in relative motion.

CHART: Force Vector Diagram Figure 4. 3: Force Vector Diagram for mass m 1.

CLICKER: For the week 4 Lab your group should conduct experiments at inclination angles relatively close to the static coefficient of friction angle. • Select your Answer: A. True B. False

CLICKER: Based on Amanton's 1 st Law we expect that the dynamic coefficient of friction will ______ the angle of inclination as it changes for each experimental trial. • Select your Answer: A. B. C. D. Be inversely related to Decrease with Be independent of Increase with

EXECUTE: Recall the Governing Equations

EXECUTE: Simplify Governing Equations Applying the assumptions to the Governing equations and evaluating generates:

EXECUTE: Simplify Governing Equations Taking inventory of the equations and unknown variables gives:

EXECUTE: Simplify Governing Equations Generating the final equations required to analyze the Kinematically Constrained Experiment gives:

EXECUTE: Simplify Governing Equations New form of equation for dynamic coefficient of friction:

TEST: Validate, Verify, and Apply Intuition to Data and Results • Compare calculated values of acceleration of both masses in addition to value for coefficient of dynamic friction. • Confirm magnitude of values and signs are in line with hypotheses • positive vs. negative velocities and accelerations • Magnitude of coefficient of dynamic friction

ITERATE: Perform multiple test runs for each group member • Each Group Member will have a unique angle of inclination • Each Group Member will perform multiple test runs with varying m 2 values

Week 4 Kinematically Constrained Linear Motion

Week 4 Kinematically Constrained Linear Motion Lab Experiment Set-Up

Homework • Prior to LAB tomorrow • Read section 4. 2 of the textbook • Watch Week 4 LAB Videos • Complete the on-line LAB quiz in my. Courses • Attempt to solve all assigned chapter problems in your logbook before RECITATION. • Week 4 Problem Set from Section 4. 5: 1 6 8 12 18 22

Exam #1 at end of week 5!! • Exam will be given Saturday, September 28 th, 2013 • The Exam is designed for 90 minutes. You will have the entire 2 hours to complete the exam. • The Exam is closed-book and closed-notes. • An Equation Sheet will be provided for you. This Equation Sheet will be included in the Week 5 Reading Assignment for your reference. • You will need a Calculator for the exam. • There will be 3 Questions as outlined below: Question 1 2 3 Description 10 Multiple Choice questions Long answer work-out problem based on content from weeks 1 - 4

Questions?

Homework • Prior to LAB tomorrow • Read section 4. 2 of the textbook • Watch Week 4 LAB Videos • Complete the on-line LAB quiz in my. Courses • Attempt to solve all assigned chapter problems in your logbook before RECITATION. • Week 4 Problem Set from Section 4. 5: 1 6 8 12 18 22 • Lab Report #3 is due Monday by 6: 00 pm! The Scribe must upload the LAB REPORT to the my. Courses Lab Report #3 Dropbox by 6: 00 pm tonight!