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ENG 243 - Statics. Introduction. Engineering Mechanics. Describe how forces affect bodies Applied Physics Equations of Motion Equations of Equilibrium Applied to real-world situations. Mechanics Courses. Statics Rigid Bodies No Acceleration. Dynamics Rigid Bodies Acceleration.
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ENG 243 - Statics Introduction
Engineering Mechanics • Describe how forces affect bodies • Applied Physics • Equations of Motion • Equations of Equilibrium • Applied to real-world situations
Mechanics Courses Statics Rigid BodiesNo Acceleration Dynamics Rigid BodiesAcceleration Strengths of Mat’ls Deformable BodiesNo Acceleration
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?
Units • 4 units – 3 basic, 1 derived • SI • 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
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
Significant Digits • Carry intermediate answers • 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: 1.237 0.243
Calculators • Basic Scientific • Sin, Cos, Tan • Square roots/Powers • Polar/Rectangular • Advanced Scientific • Simultaneous Equations • Vectors – Cross Products
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
2 m 350 mm 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. 1. Sketch 2. Given: 3. Find:
2 m 350 mm 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. 4. Primary equation 5. Secondary equations 6. Rewrite to solve
2 m 350 mm 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. 7. Plug in numbers and units 8. Check that you’ve solved the problem