Engineering 91.111 Mechanics I

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Engineering 91.111Mechanics I

• Section B
• Prof. S.J. Kennedy

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Course Information
TEXT. Engineering Mechanics. Statics and Dynamics
8th Ed. R.C. Hibbeler. Prentice-Hall
1998.
INSTRUCTOR 91.111B Prof. S.J. Kennedy
3064 MC
Ph. 520-5793
LECTURES 91.111B Theatre B
Monday 1130 AM
Tuesday 130 PM
Thursday 1230
PM
PROBLEM ANALYSIS 230 PM to 530 PM
First hour Instruction Second
hour Q/A Third hour Test
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Course Information (cont.)
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Solution Presentation

• Simple statement of problem
• Include sketch where applicable
• State assumptions
• Make additional sketches to clarify problem
  solution
• Simple geometric calculations to the right of
  sketch

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Solution Presentation (cont.)

• State Principles and show formulae
• indicate results of intermediate steps
• Repeat final answers near the right edge, under
  or beside the final step
• Mark it clearly as the answer
• Use the following
• Pencil
• Eraser
• Straightedge

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Solution Presentation (cont.)

• Be NEAT!
• Show significant digits
• Final answers 3 or 4 digits
• Intermediate results to 4 or 5
• Show units of measure
• Use Quad (engineering) paper

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Example Solution
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Introduction

• Mechanics of rigid bodies
• Statics acted on by balanced forces and are at
  rest or have uniform motion.
• Kinematics concerned with the motion of bodies
  without considering the manner in which the
  motion is produced.
• Kinetics concerned with bodies that are acted
  on by unbalanced forces and have non-uniform or
  accelerated motions.

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Introduction (cont.)

• Mechanics of deformable bodies
• Mechanics of fluids

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Newtons Laws of Motion

• Law 1
• In the absence of external forces, a particle
  originally at rest or in motion with a constant
  velocity will remain at rest or continue to move
  with a constant velocity along a straight line

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Newtons Laws of Motion

• Law 2
• If an external force acts on a particle, the
  particle will be accelerated in the direction of
  the force and the magnitude of the acceleration
  will be directly proportional to the force and
  inversely proportional to the mass of the
  particle.
• Fma

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Newtons Laws of Motion

• Law 3
• For every action there is an equal and opposite
  reaction. The forces of action and reaction
  between contacting bodies are equal in magnitude,
  opposite in direction, and collinear.
• From this Newton formulated the Law of
  Gravitation, the law that governs the mutual
  attraction between two isolated bodies.

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Newtons Laws of Motion

• Where
• F is the magnitude of the mutual force of
  attraction between the two bodies
• G is the universal gravitational constant
  6.673x10-11 m3/kgs2

m2
m1
r
F Gm1m2/r2
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Mass and Weight

• Mass (m, units kg.) of a body is an absolute
  quantity and is independent of the position of
  the body.
• Weight (W, units N.) of a body is the
  gravitational attraction exerted on the body by
  another body such as the earth.

WGmem/re

• Where
• me is the mass of the earth
• re is the mean radius of the earth

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Units of Measurement
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Units of Measurement

• Derived units include area, volume,linear or
  angular velocity, acceleration, frequency,
  density, force, stress, pressure, etc.
• Engineers express
• linear measurements in mm.
• Force in KN.
• Stress and Pressure in MPa.

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Additional Material

• Read Sections 1.1-1.6
• Problems Section 1
• 1,8,13,15,16