1. ENG Statics
Introduction

2. Engineering Mechanics
Describe how forces affect bodies
Applied Physics
Equations of Motion
Equations of Equilibrium
Applied to real-world situations

3. Mechanics Courses Statics Rigid Bodies No Acceleration Dynamics
Rigid Bodies Acceleration
Strengths of Mat’ls
Deformable Bodies No Acceleration

4. Crane Example How does the crane cable affect the object?
If the box moves first, what happens?
If the crane moves first, what happens?
What forces affect the crane boom?

5. Units 4 units – 3 basic, 1 derived SI USC Mass – kg Length – m
Time – s
Force – derived
F = m·a
W = m·g
1 kg·m/s2 = 1 N
USC
Force – lb
Length – ft
Time – s
Mass – derived
m = F/a
m = W/g
1 lb/ft/s2 = 1 slug

6. Units Be careful with conversions SI: g = 9.81 m/s2
Determine the weight of a 15-kg block
USC: g = 32.2 ft/s2
Determine the mass of a 200-lb block

7. Significant Digits Carry intermediate answers Round off last answer
Carry at least one extra digit
Don’t round exact numbers – trig functions
Round off last answer
If the answer begins with 1, show 4
For all others, show 3
Example:  0.243

8. Calculators Basic Scientific Advanced Scientific Sin, Cos, Tan
Square roots/Powers
Polar/Rectangular
Advanced Scientific
Simultaneous Equations
Vectors – Cross Products

9. Problem Solving Sketch Given: Find: Primary relationship (equation)
Secondary relationships, assumptions
Rewrite to final form
Plug in numbers and units
Check that you’ve solved the problem

10. Example Problem
A concrete column has a diameter of 350 mm and a length of 2 m. If the density of concrete is 2.45 Mg/m3, determine the weight of the column, in pounds.
2 m
350 mm
1. Sketch
2. Given:
3. Find:

11. Example Problem
A concrete column has a diameter of 350 mm and a length of 2 m. If the density of concrete is 2.45 Mg/m3, determine the weight of the column, in pounds.
2 m
350 mm
4. Primary equation
5. Secondary equations
6. Rewrite to solve

12. Example Problem
A concrete column has a diameter of 350 mm and a length of 2 m. If the density of concrete is 2.45 Mg/m3, determine the weight of the column, in pounds.
2 m
350 mm
7. Plug in numbers and units
8. Check that you’ve solved the problem