ME 221 Statics

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ME 221 StaticsLecture 8Sections 2.9 2.10
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Homework

• Due Monday, January 27
• Chapter 2 problems
• 61, 64, 70, 71, 72, 82, 86, 94, 105 113
• Grades posted in Blackboard
• HW 1 Quiz 1 (and solutions)
• HW 2 Quiz 2 soon (solutions posted)
• HW 3 solutions to be posted late Monday

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Exam 1

• Wednesday, January 29

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Particle Equilibrium

• For a particle to be in equilibrium, the
  resultant of the forces acting on it must sum to
  zero.

• This is essentially Newtons second law with the
  acceleration being zero.

• In equation form SF 0

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Representing Equilibrium
Vector Diagram
Vector Equation
R F1 F2 F3 F4 0
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Representing Equilibrium
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Statically Determinate

• For 3-D equilibrium, there are three scalar
  equations SFx 0 , SFy 0 , SFz 0

• Problems with more than three unknowns cannot be
  solved without more information, and such
  problems are called statically indeterminate.

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Free-body Diagram

• A free-body diagram is a pictorial representation
  of the equation SF 0 and has

• all of the forces represented in their proper
  sense and location

• indication of the coordinate axes used in
  applying SF 0

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ME 221 Exam 1 Topics

• All of Chapters 1 2 except 2.11 Springs
• Newtons Laws
• Units
• Scalars vectors defining, adding, etc.
• Laws of sine cosine
• Resolution of a vector into components
• 3D coordinates unit base vectors

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Exam 1 Topics continued

• Directional cosines
• Components of a vector in nonorthogonal terms
• Scalar products of two vectors
• 2-D and 3-D equilibrium problems
• draw a good free-body diagram

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