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Devil physics The baddest class on campus Pre-DP Physics

Devil physics The baddest class on campus Pre-DP Physics. Chapter 9, Bodies in Equilibrium: Elasticity and Fracture. 9-1: Statics – The Study of Forces in Equilibrium 9-2: The Conditions for Equilibrium 9-3: Solving Statics Problems 9-4: Applications to Muscles and Joints

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Devil physics The baddest class on campus Pre-DP Physics

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  1. Devil physicsThe baddest class on campusPre-DP Physics

  2. Chapter 9, Bodies in Equilibrium: Elasticity and Fracture • 9-1: Statics – The Study of Forces in Equilibrium • 9-2: The Conditions for Equilibrium • 9-3: Solving Statics Problems • 9-4: Applications to Muscles and Joints • 9-5: Stability and Balance • 9-6: Elasticity: Stress and Strain • 9-7: Fracture • 9-8: Spanning a Space: Arches and Domes

  3. Chapter 9, Bodies in Equilibrium: Elasticity and Fracture • 9-1: Statics – The Study of Forces in Equilibrium • 9-2: The Conditions for Equilibrium • 9-3: Solving Statics Problems No New Equations!!!

  4. Chapter 9, Bodies in Equilibrium: Elasticity and Fracture • This chapter is devoted to the Future Engineers of America • Engineers must ensure the structure is capable of withstanding all the forces acting on it • If your bodies aren’t in equilibrium, you will have elasticity and/or fracture!

  5. Objectives • Explain the meaning of the term static equilibrium • Understand the correlation between Newton’s Second Law and static equilibrium • Name the first condition for equilibrium (which is really three conditions) • Name the second condition for equilibrium • Solve problems involving static equilibrium

  6. Static Equilibrium • Statics – the study of forces in equilibrium • Equilibrium – Latin for equal forces or balance • The study of forces acting on and within bodies that are in equilibrium • This, in turn leads to a study of whether or not the structure is capable of withstanding the forces without deformation or fracture

  7. Newton’s Second Law • Sum of the Forces equals mass times acceleration • If the forces are in equilibrium, the sum of the forces equals zero and there is no acceleration • Constant velocity • No motion

  8. Static Equilibrium FN Fg

  9. Static Equilibrium • Now What?

  10. Static Equilibrium • First Condition for Equilibrium (which is really three)

  11. Static Equilibrium • What forces are at work here?

  12. Static Equilibrium • What forces are at work here? FT-1 Fg FT-2

  13. Static Equilibrium FT-1 Fg FT-2

  14. Static Equilibrium FT-1-x FT-1-y FT-1 Fg FT-2

  15. Static Equilibrium FT-1-x  FT-1-y FT-1 Fg FT-2

  16. Static Equilibrium FT-1-x  FT-1-y FT-1 Fg FT-2

  17. Static Equilibrium FT-1-x  FT-1-y FT-1 Fg FT-2

  18. Static Equilibrium • Piece a’ cake, right? • Well, if you don’t feel a little torqued by now, you will shortly

  19. Static Equilibrium Fg-B Fg-T FN FN

  20. Static Equilibrium • Now What? Fg-T FN-1 Fg-B FN-2

  21. Static Equilibrium • Second condition of equilibrium

  22. Static Equilibrium Fg-T FN-1 Fg-B FN-2

  23. Static Equilibrium FT  • What is FT? FW ??? Fg-1 Fg-2

  24. FT-x Static Equilibrium FT-y FT  FW Fg-1 Fg-2

  25. FT-x Static Equilibrium FT-y FT  FW Fg-1 Fg-2 Note: The wall exerts a force on the beam that would have to be considered in a ΣF equation, but we can eliminate it by using Στ and making the attachment point our reference point.

  26. FT-x  Static Equilibrium FT-y FT  Fg-1 Fg-2

  27. FT-x Static Equilibrium FT-y FT  Fg-1 Fg-2

  28. Solving Problems with Statics • Choose one body at a time and draw free-body diagram showing all forces acting on it • Resolve all forces into their x-y components. • Write down equations for ΣFx = 0, ΣFy = 0, Στ = 0.

  29. Solving Problems with Statics • For Στ = 0, choose a reference point for determining moment arms and ensure all forces have components perpendicular to the moment arm. Determine direction of torque for each force and assign +/- to CW/CCW. Note: If you choose one of your unknowns as your reference point, you eliminate it from the torque equation because its distance (r) is zero.

  30. Solving Problems with Statics • Solve equations for unknowns. Since you have three equations, you can solve for three unknowns. Some of these unknowns may be components of a force. Use trigonometry to determine a force from its components and angles. Note: If any answer comes out to be negative, it’s okay. It just means the force is acting in a direction opposite to the one you originally assigned to it.

  31. Solving Problems with Statics • Example 9-7 • Figure 9-11 • Example 9-8 • Example 9-9

  32. ΣaryReview • Can you explain the meaning of the term static equilibrium? • Do you understand the correlation between Newton’s Second Law and static equilibrium? • Can you name the first condition for equilibrium (which is really three conditions)? • Can you name the second condition for equilibrium? • Can you solve problems involving static equilibrium?

  33. Questions?

  34. Homework Part A, #1-14 Part B, #15-27

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