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Copyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Chapter 6. Dynamics I: Motion Along a Line Chapter 6. Dynamics I: Motion Along a Line Chapter Goal: To learn how to solve problems about motion in a straight line. Copyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Student Learning Objectives Ch. 6 To draw and make effective use of free-body diagrams. To recognize and solve simple equilibrium problems. To distinguish mass, weight, and apparent weight. To learn and use simple models of friction. To apply the full strategy for force and motion problems to problems in single-particle dynamics. Copyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Equilibrium An object on which the net force is zero is said to be in equilibrium . Static equilibrium : object is at rest. Dynamic equilibrium : moving along a straight line with constant velocity. Both are identical from a Newtonian perspective because the net force and the acceleration are zero. Copyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Problem-Solving Strategy: Equilibrium Problems Copyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Problem-Solving Strategy: Equilibrium Problems Copyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Example Equilibrium Problem (#31) A 500 kg piano is being lowered into position by a crane while 2 people steady it with ropes pulling to the side. Bobs rope pulls left, 15 below horizontal, with 500 N of tension. Ellens rope pulls right, 25 below horizontal. a. What tension must Ellen maintain in her rope to keep the piano descending at a steady speed? b. What is the tension in the main cable? Copyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Example Problem (#31) Freebody Diagram T 3 T 1 is Bobs side, T 2 is Ellens side, T 3 is the main cable. Same system for the angles Copyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Problem #31 - Apply Newtons 1 st Law F y = 0, F x = 0 T 3 Copyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Problem #31 Solve and assess T 2 = 533 N, T 3 = 5.25 x 10 3 N. The cable must supports the weight of the piano (4900 N) plus the added downward components of the tension in the supporting ropes. Copyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Using Newtons 2 nd Law: Workbook exercises 5-12 Copyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Using Newtons 2 nd Law: Workbook exercises Answers 5-6-F 3 sin Copyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.... View Full Document