An object in mechanical equilibrium is stable, without changes in motion.

1. An object in mechanical equilibrium is stable, without changes in motion.

2. Question: Warm UP • How can you change an object’s state of motion?

3. Question: Warm UP • How can you change an object’s state of motion? • Answer: An unbalanced force is needed to change an object’s state of motion.

4. 2.1Force Net Force A force is a push or a pull. To change the motion of an object, you need an unbalanced force. A force of some kind is always required to change the state of motion of an object. The combination of all forces acting on an object is called the net force. The net force on an object changes its motion. The scientific unit of force is the newton, abbreviated N.

5. How Forces affect Motion • Make things start moving. • Make objects move faster. • Make objects move slower. • Make objects stop moving. • Make Objects change direction. • Make objects change shape.

6. Force Facts • Forces are measured in Newtons, (N). • Forces act in pairs. • Forces act in a particular direction. • Forces usually cannot be seen, but their effects can. • Science uses vectors to visualize the magnitude and direction of forces.

7. Common forces that affect motion of objects. • Mechanical, including friction • Electrical charges • Nuclear • Magnetic • Elastic-spring • Heat • wind • Chemical

8. 2.1Force Net Force When the girl holds the rock with as much force upward as gravity pulls downward, the net force on the rock is zero.

9. 2.1Finding Net force of an object The table pushes up on the book with as much force as the downward weight of the book. The net force of the book is zero.

10. 2.1Force Showing Forces using Force Vectors A vectoris an arrow that represents the magnitude and direction of a force. A vector quantity needs both magnitude and direction for a complete description. Force is an example of a vector quantity.

11. Drawing 1-D force vectors • A vector is drawn using an arrow. The length of the arrow indicates the magnitude of the vector. The direction of the vector is represented by no surprisingly, the direction of the arrow. • Magnitude is the strength of the force, measured in Newton’s here. • Direction in this class is U, D, L & R.

12. Warm-Up Question (Vectors) • An object has a mass of 500 g. • What is the weight (force) in Newton’s of the 500 g mass? Predict and then measure using a spring scale. • How do you Draw a vector that shows both the magnitude and direction of the 500 g mass accurately. Predict and explain and then draw. • Scale is 1cm = 1Newton

13. Warm-Up Question Solution • An object has a mass of 500 g. • What is the force in Newton’s of the mass? • 5 Newton’s • Draw a 1-dimensional vector of the force, with both magnitude and direction. • Scale is 1cm = 1Newton • 5 cm long arrow, 5 N magnitude, downward direction

14. 2.1Force Force Vectors 1 cm = 20 N This vector represents a force of 60 N to the right.

15. Draw Vectors of these masses on Graph sheet. Activity: Hang mass using spring scale, find the force in Newton's, (N), and then draw vectors for each mass on piece of graph paper. Make sure to draw the arrow tail (beginning) and head (end) of each vector. 100 g = 1 N 1 N = 1 cm

16. 55 Kg man! 1Kg = 1N 10 N = 1cm 1. Identify the two types of forces acting on this man as he hangs in the air cleaning windows.2. What is the net force on this man?

17. 1. Identify the two types of forces acting on this guy up in the air. How many vectors? Explain Upward force & downward force. The force due to tension on the rope holding man up, and the weight of the man due to gravity.

18. Write down these words and definitions

19. Write down these words and definitions • Mechanical equilibrium: When the sum of all forces on an object is equal to zero; no change in motion or at rest! • Displacement: The difference between the initial position (start)of an object and any later position (end).

20. Chapter 2Support Force-Warm up The table pushes up on the book with as much force as the downward weight of the book. This book has 5 N downward force (weight) due to gravity. What is the upward force (support force)? Explain What is the resultant force? Explain ? N 5 N

21. Chapter 2 Support Force-Warm up The table pushes up on the book with as much force as the downward weight of the book. This book has 5 N downward force due to gravity. What is the upward force? Explain 5N U, 5N D What is the resultant force? Explain 0N, no Direction +5N -5N +5N + (-5N) = 0N

22. Force Net Force The net force depends on the magnitudes and directions of the applied forces. ∑ = sum Net force is, ∑ Forces = ?

23. Force Net Force The net force depends on the magnitudes and directions of the applied forces.

24. Force Net Force The net force depends on the magnitudes and directions of the applied forces.

25. Force Net Force The net force depends on the magnitudes and directions of the applied forces.

26. Force Net Force The net force depends on the magnitudes and directions of the applied forces.

27. Force Net Force The net force depends on the magnitudes and directions of the applied forces.

28. Force Tension and Weight A stretched spring is under a “stretching force” called tension. Pounds and Newton's are units of weight, which are units of force.

29. Force Tension and Weight The upward tension in the string has the same magnitude as the weight of the bag, so the net force on the bag is zero. The bag of sugar is attracted to Earth with a gravitational force of 2 pounds or 9 newtons.

30. Force Tension and Weight There are two forces acting on the bag of sugar: • tension force acting upward • weight acting downward The two forces on the bag are equal and opposite. The net force on the bag is zero, so it remains at rest.

31. Force Force Vectors

32. Bridges and Forces • Objective: I will understand how forces are distributed in real world structures, such as bridges. I will design a bridge that must withstand the greatest force among all groups in class!

33. Question: • What was the greatest force your bridge design held up today with or without collapsing? • What basic bridge type held the most forces before collapsing, if it did collapse?

34. Force How can you change an object’s state of motion?

35. Q. Dropping supplies, a plane flies 700 km west one day. The next day it flies 600 km east. Then it flies 300 km west and on the next day 400 km east. How far away is theplane from where it first began? Question of the day-Exit ticket • 0 km away • Adding vectors to find resultant vector! • 1 cm = 100 km • Dropping supplies, a plane flies 700 km west one day. The next day it flies 600 km east. Then it flies 300 km west and on the next day 400 km east. How far away (displacement) is the plane from where it first began? Explain!

36. Question of the Day

37. Question of the Day-Warm-upPrediction and then Verify.

38. Question of the Day-Warm-upAnswer and SolutionC, D, A=B

39. Question of the day • For an object to be in equilibrium, what must be true? • The painters and scaffolding are in equilibrium, so what is the unknown force acting downward?

40. Question of the day Solution • For an object to be in equilibrium, what must be true? Things must be steady, nothing is changing. • The painters and scaffolding are in equilibrium, so what is the unknown force acting downward? 400 N • The sum of the upward vectors equals the sum of the downward vectors is , & is in static equilibrium.

41. LOVE Card Review • Please take out LOVE cards. • Or make LOVE cards if you lost them. • Quiz each other for 5-minutes. • Matching, verbal, study quietly, etc.. • I will stop by and give each student a grade for completing your cards.

42. 2.2Mechanical Equilibrium What is the Mechanical Equilibrium rule?

43. 2.2Mechanical Equilibrium Mechanical equilibrium is a state oif steadiness, and nothing is changing. Whenever the net force on an object is zero, the object is in mechanical equilibrium—this is known as the equilibrium rule.

44. 2.2Mechanical Equilibrium • The  symbol stands for “the sum of.” • F stands for “forces.” For a suspended object at rest, the forces acting upward on the object must be balanced by other forces acting downward. The vector sum equals zero.

45. 2.2Mechanical Equilibrium The sum of the upward vectors equals the sum of the downward vectors. F = 0, and the scaffold is in equilibrium.

46. 2.2Mechanical Equilibrium The sum of the upward vectors equals the sum of the downward vectors. F = 0, and the scaffold is in equilibrium.

47. 2.2Mechanical Equilibrium think! If the gymnasthangs with her weight evenly divided between the two rings, how would scale readings in both supporting ropes compare with her weight? Suppose she hangs with slightly more of her weight supported by the left ring. How would a scale on each rope read?

48. 2.2Mechanical Equilibrium think! If the gymnasthangs with her weight evenly divided between the two rings, how would scale readings in both supporting ropes compare with her weight? Suppose she hangs with slightly more of her weight supported by the left ring. How would a scale on the right read? Answer:In the first case, the reading on each scale will be half her weight.

49. 2.2Mechanical Equilibrium You can express the equilibrium rule mathematically as F = 0.

50. Question of the Day-Warm-up Where does the garbage can need to be located so the see-saw will be level and in mechanical equilibrium? Show your work and all units..