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N e w t o n’ s L a w s

N e w t o n’ s L a w s. Unit 3. 3.1 Force and Mass. Force – push or pull; required to change an object’s motion. Vector – so magnitude and direction Example of Contact Forces Friction Tension Applied Spring. Examples of Field Forces Gravitational Electric Magnetic.

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N e w t o n’ s L a w s

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  1. Newton’sLaws Unit 3

  2. 3.1 Force and Mass

  3. Force – push or pull; required to change an object’s motion. Vector – so magnitude and direction Example of Contact Forces Friction Tension Applied Spring Examples of Field Forces Gravitational Electric Magnetic 3.1 Force and mass

  4. Mass – measurement of how difficult it is to change the objects velocity Inertia – resistance to change in velocity So mass is a measurement of an object’s inertia 3.1 Force and mass

  5. 3.2 Newton’s First Law of Motion

  6. 1st Law An object at rest remains at rest as long as no net force acts on it. An object moving with constant velocity continues to move with the same speed and in the same direction as long as no net force acts on it. 3.2 Newton’s First Law of Motion

  7. Sometimes called the Law of Inertia 3.2 Newton’s First Law of Motion

  8. 3.3 Newton’s Second Law of Motion

  9. 2nd Law A net force causes an acceleration in the direction of the net force. Simulation 3.3 Newton’s Second Law of Motion

  10. N W Free body diagrams Show all the forces acting on an object For example an object sitting on a table W – weight = mg N – Normal Force (perpendicular) to the surface 3.3 Newton’s Second Law of Motion

  11. N T W Free body diagrams If a rope pulls the object toward the right, then T = Tension Practice Free Body 3.3 Newton’s Second Law of Motion

  12. Free body diagrams • Steps in problems solving • Sketch the forces • Isolate the Object • Choose a Coordinate System • Resolve the Forces into Components • Apply Newton’s Second Law of Motion 3.3 Newton’s Second Law of Motion

  13. A 50 kg gopher has a string tied around his neck and pulled with a force of 80 N at an angle of 30o to the horizontal. What is his acceleration? 3.3 Newton’s Second Law of Motion

  14. A 50 kg gopher has a string tied around his neck and pulled with a force of 80 N at an angle of 30o to the horizontal. What is his acceleration? Free Body diagram 3.3 Newton’s Second Law of Motion

  15. A 50 kg gopher has a string tied around his neck and pulled with a force of 80 N at an angle of 30o to the horizontal. What is his acceleration? Free Body diagram N T 3.3 Newton’s Second Law of Motion W

  16. A 50 kg gopher has a string tied around his neck and pulled with a force of 80 N at an angle of 30o to the horizontal. What is his acceleration? Free Body diagram Axis N T 3.3 Newton’s Second Law of Motion W

  17. A 50 kg gopher has a string tied around his neck and pulled with a force of 80 N at an angle of 30o to the horizontal. What is his acceleration? Free Body diagram Axis Ty N T 3.3 Newton’s Second Law of Motion Tx W

  18. A 50 kg gopher has a string tied around his neck and pulled with a force of 80 N at an angle of 30o to the horizontal. What is his acceleration? Free Body diagram Axis Equation Ty N 3.3 Newton’s Second Law of Motion Tx W

  19. 3.4 Newton’s Third Law of Motion

  20. For every force that acts on an object, there is a reaction force acting on a different object that is equal in magnitude and opposite in direction. If object 1 exerts a force F on object 2, then object 2 exerts a force –F on object 1. 3.4 Newton’s Third Law of Motion

  21. What are the action reaction pairs in the following? 3.4 Newton’s Third Law of Motion

  22. A 60 kg man walks off a 3 m long canoe by walking from one end to the other. He applies a force of 20 N to the canoe, which has a mass of 150 kg. • What is the acceleration of • the man? • B. What is the acceleration of the canoe? 3.4 Newton’s Third Law of Motion

  23. A 60 kg man walks off a 3 m long canoe by walking from one end to the other. He applies a force of 20 N to the canoe, which has a mass of 150 kg. Free Body Diagrams Nc Nm 3.4 Newton’s Third Law of Motion P P Wm Wc

  24. A 60 kg man walks off a 3 m long canoe by walking from one end to the other. He applies a force of 20 N to the canoe, which has a mass of 150 kg. Equations Nc Nm 3.4 Newton’s Third Law of Motion P P Wm Wc

  25. A 60 kg man walks off a 3 m long canoe by walking from one end to the other. He applies a force of 20 N to the canoe, which has a mass of 150 kg. A-acceleration of man Nc Nm 3.4 Newton’s Third Law of Motion P P Wm Wc

  26. A 60 kg man walks off a 3 m long canoe by walking from one end to the other. He applies a force of 20 N to the canoe, which has a mass of 150 kg. A – acceleration of canoe Nc Nm 3.4 Newton’s Third Law of Motion P P Wm Wc

  27. Two boxes are tied together with a rope, and the first one is pulled by a second rope. Both boxes accelerate at 2.0 m/s2. If the front box has a mass of 25 kg, and the second a mass of 50 kg, what is the tension on each rope? a 3.4 Newton’s Third Law of Motion

  28. Nb Nf T2 T1 T2 Wf Free body diagrams 3.4 Newton’s Third Law of Motion Wb

  29. Nb Nf T2 T1 T2 Wf Equations Solve (add) 3.4 Newton’s Third Law of Motion Wb

  30. 3.5 The Vector Nature of Forces

  31. Forces are vectors, so they can be treated using vectors rules 3.5 The Vector Nature of Forces

  32. L B W Two men are carrying a 1.3 kg pail of water, the first dude (Bob) exerts a force of 7N, and the second one (Leon) exerts a force of 11N @ 28o. What is the angle of Bob’s force? Free Body Diagram? 3.5 The Vector Nature of Forces

  33. Two men are carrying a 1.3 kg pail of water, the first dude (Bob) exerts a force of 7N, and the second one (Leon) exerts a force of 11N @ 28o. What is the angle of Bob’s force? Components? L B By 3.5 The Vector Nature of Forces Bx W

  34. Two men are carrying a 1.3 kg pail of water, the first dude (Bob) exerts a force of 7N, and the second one (Leon) exerts a force of 11N @ 28o. What is the angle of Bob’s force? Components? Ly L By 3.5 The Vector Nature of Forces Bx Lx W

  35. Two men are carrying a 1.3 kg pail of water, the first dude (Bob) exerts a force of 7N, and the second one (Leon) exerts a force of 11N @ 28o. What is the angle of Bob’s force? Equations? Ly By 3.5 The Vector Nature of Forces Bx Lx W

  36. Two men are carrying a 1.3 kg pail of water, the first dude (Bob) exerts a force of 7N, and the second one (Leon) exerts a force of 11N @ 28o. What is the angle of Bob’s force? Values? Ly By 3.5 The Vector Nature of Forces Bx Lx W

  37. Two men are carrying a 1.3 kg pail of water, the first dude (Bob) exerts a force of 7N, and the second one (Leon) exerts a force of 11N @ 28o. What is the angle of Bob’s force? Values? Ly By 3.5 The Vector Nature of Forces Bx Lx W

  38. Two men are carrying a 1.3 kg pail of water, the first dude (Bob) exerts a force of 7N, and the second one (Leon) exerts a force of 11N @ 28o. What is the angle of Bob’s force? Solve? Ly By 3.5 The Vector Nature of Forces Bx Lx W

  39. Two men are carrying a 1.3 kg pail of water, the first dude (Bob) exerts a force of 12.3N, and the second one (Leon) exerts a force of 11N @ 28o. What is the angle of Bob’s force? Solve? Ly By 3.5 The Vector Nature of Forces Bx Lx W

  40. 3.6 Frictional Forces

  41. Friction – force that opposes motion Caused by microscopic irregularities of a surface Increases as pushing force increases 3.6 Frictional Forces

  42. Depends on the normal force and the type of surface f – force of friction (N) N – normal force m – coefficient of friction (1 or less) 3.6 Frictional Forces

  43. Three types of friction • Static – object at rest • Kinetic – object in motion • 3.Rolling – just like it sounds 3.6 Frictional Forces

  44. Example 3.6 Frictional Forces

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