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 3rd 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, m1 and m2, and an ideal pulley, P.
The masses m1 , m2 , and pulley P interact by means of an ideal
cable.
• The first mass m1 is positioned on a rough-surface ramp inclined at
an angle to the horizontal. The ideal cable connects from mass
m1 over the ideal (frictionless) pulley P to m2 .
• The second mass m2 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
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: Free Body Diagrams
Figure 4.2: Free Body Diagrams for a pulley assembly and
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: Free Body Diagrams
Figure 4.2: Free Body Diagrams for a pulley assembly and
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: 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 m1.
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: 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 1st 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
CLICKER: Based on Amanton's 1st 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 m2 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 myCourses
• 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 28th, 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
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 myCourses
• 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 6:00pm!
The Scribe must upload the LAB REPORT to the myCourses
Lab Report #3 Dropbox by 6:00pm tonight!