McColgan– New Groups!
•  Table 1
–  Brendan
–  Debbie
–  Mike
–  Matt T
–  Rik
–  Edgar
•  Table 3
–  Lindsay
–  Kristen
–  Jack
–  Sarah
–  Shane
–  Tom
•  Table 2
–  River
–  Ashlee
–  Kulsum
–  Cody
–  David
–  Adam
•  Table 4
–  Garry
–  Ryan
–  Joey
–  Brian
–  Matt D
Moustakas – New Groups!
•  Table 1
–  Olivia
–  Lauren
–  Alex
–  Lisa
–  Shannon
–  Jacob
•  Table 4
–  Meghan
–  Kori
–  Robert
–  Amanda
–  Matt P.
•  Table 2
–  Matt M.
–  Corinne
–  Connor
–  Emily
–  Chris
–  Katelyn
•  Table 3
–  Christy
–  Jesus
–  Elizabeth
–  Andrew
–  Luis
Fermi Problem #1
How many golf balls would it take to
circle the Earth at the equator?
•  Explicitly state all your (hopefully reasonable!) assumptions.
Show all your work, including units!
•  There is no “right” answer? Estimate everything within an
order of magnitude.
•  Write down who you worked with, roughly how long you
spent, and what numbers you looked up, if any.
•  Due Thursday 10/11.
Introduction to Forces – Ch. 5
•  Types of forces
•  Identifying forces
–  Interaction Diagrams
•  Free Body Diagrams
•  Newton’s First and Second Laws
•  Linking Forces and Motion
Important Concepts
A Short Catalog of Forces
A Short Catalog of Forces
A Short Catalog of Forces
A Short Catalog of Forces
A Short Catalog of Forces
A Short Catalog of Forces
A Short Catalog of Forces
Key Skills
Tactics: Identifying forces
Key Skills
Tactics: Drawing a free-body diagram
EXAMPLE 5.4 An elevator accelerates
upward
EXAMPLE 5.5 An ice block shoots across a
frozen lake
General Principles
General Principles
Important Concepts
Important Concepts
Activities and Problems
•  Free Body Diagram of Book on Table
•  Workbook
•  pp. 5-1 to 5-8
Upcoming Assignments
•  MasteringPhysics online HW due tonight, Thursday
10/4 by 11 pm
•  Read Chapter 6 to the end by Tuesday 10/9
•  Pre-class MasteringPhysics assignment due before
class on Tuesday 10/9
•  MasteringPhysics online HW due, Thursday 10/11 by
11 pm
Questions
1. What is a “net force?”
A.  The weight excluding the container
B.  The vector sum of all forces in a
problem
C.  The vector sum of all forces acting
on an object
2. Which of the following are steps used to
identify the forces acting on an object?
A.  Draw a closed curve around the system.
B.  Identify “the system” and “the
environment”.
C.  Draw a picture of the situation.
D.  The vector force applied by a net
D.  All of the above.
E.  The vector sum of all forces that add
E.  None of the above.
up to zero
Questions
3. Which of these is not a force
discussed in this chapter?
4. What is the name of a diagram used to
show all forces acting on an object?
A.  The tension force
A.  Motion diagram
B.  The orthogonal force
B.  Interaction diagram
C.  The normal force
C.  Free-body diagram
D.  The thrust force
D.  Second-law diagram
E.  None of the above
What is a “net force?”
A.  The weight excluding the container
B.  The vector sum of all forces in a problem
C.  The vector sum of all forces acting on an object
D.  The vector force applied by a net
E.  The vector sum of all forces that add up to zero
Which of the following are steps used to
identify the forces acting on an object?
A.  Draw a closed curve around the system
B.  Identify “the system” and “the environment”
C.  Draw a picture of the situation
D.  All of the above
E.  None of the above
Which of these is not a force discussed in
this chapter?
A.  The tension force
B.  The orthogonal force
C.  The normal force
D.  The thrust force
E.  None of the above
What is the name of a diagram used to
show all forces acting on an object?
A.  Motion diagram
B.  Interaction diagram
C.  Free-body diagram
D.  Second-law diagram