Force-and-Motion_Session-03_Uniform-Circular-Motion.pptx

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1. REGIONAL K to 10 TRAINING of TEACHERS (RTOT) on CRITICAL CONTENT in GRADE 8 SCIENCE JUNE 24 – JULY 6, 2018 Punta Villa Resort, Villa Arevalo, Iloilo City

2. Grade 8 Science Force, Motion and Energy Session 3: Uniform Circular Motion Learning Facilitator: ROMARK JOHN B. JEREZ Faculty, Jaro National High School Division of Iloilo City [email protected]

3. Grade 8 Learning Competencies in Force, Motion and Energy relate the laws of motion to bodies in uniform circular motion (S8FE-Ib-18); infer that circular motion requires the application of constant force directed toward the center of the circle (S8FE-Ib-19)

4. According to recent local research (Lorenzana and Roleda, 2017), Grade 8 students believed that: Objects in circular motion will continue in circular motion if centripetal force is removed.

5. Session Objectives: describe the motion of an object moving in a circular path determine the direction of the force, acceleration and velocity of an object moving around a circular path using diagrams

6. Session Objectives (cont’d) explain the relationship between the centripetal force and the speed/velocity of an object moving in UCM explain the relationship between the speed/velocity of an object moving in UCM and the radius of the circular path

7. Recall: Determine which among Newton’s three laws would apply to the following situation. Newton’s First Law Newton’s Second Law Newton’s Third Law DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

8. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT NEWTON’S FIRST LAW NEWTON’S SECOND LAW NEWTON’S THIRD LAW

9. 1. When you dive off of a diving board, you push down on the springboard. The board springs back and forces you into the air DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

10. 1. When you dive off of a diving board, you push down on the springboard. The board springs back and forces you into the air DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT ANSWER: C. Newton’s Third Law

11. 2. You are driving your car at a very high speed and hit something, like a brick wall or a tree, the car will come to an instant stop, but you will keep moving forward. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

12. 2. You are driving your car at a very high speed and hit something, like a brick wall or a tree, the car will come to an instant stop, but you will keep moving forward. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT ANSWER: A. Newton’s First Law

13. 3. It is easier to push an empty shopping cart than a full one, because the full shopping cart has more inertia (mass) than the empty one. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

14. 3. It is easier to push an empty shopping cart than a full one, because the full shopping cart has more inertia (mass) than the empty one. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT ANSWER: B. Newton’s Second Law

15. When an object is acted upon by a net force, it accelerates – it changes its state of motion. So when a force acts on an object, the following may happen: It moves from being at rest It stops from being in motion It changes its speed (speed up or slow down) DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

16. When an object is acted upon by a net force, it accelerates – it changes its state of motion. So when a force acts on an object, the following may happen: It moves from being at rest It stops from being in motion It changes its speed (speed up or slow down) Maintains constant speed but changes its direction DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

17. Watch a video on the “Wall of Death”. Answer the following question: - How are the daredevils able to perform the “Wall of Death” stunt? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

18. “Wall of Death” DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT http://2.bp.blogspot.com/-b9UgPo6j_JU/Uygi1FhDzvI/AAAAAAAASqo/ofAAITs3y0g/s1600/38.jpg

19. How are the daredevils able to perform the “Wall of Death” stunt? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

20. Jackstone Ball Lift Challenge The task of the group is to lift the Jackstone ball for 20 seconds with an inverted wide-mouthed jar. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

21. W hat enabled you to transfer the ball without touching the ball ? What kind of motion is required to transfer the ball ? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

22. Is it necessary to sustain the motion of the ball inside the jar to keep it from falling? What would happen to the ball if this motion suddenly stopped? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

23. As the ball moves around the jar, how many forces are acting on it? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT Draw the forces acting on the ball while moving inside the jar by constructing FBD. (Specify if your FBD is a top view or a side view.)

24. Based on your Free-Body Diagram: What forces are acting on the ball? Is there a NET FORCE acting on the ball? If yes, what is that NET FORCE? If no, why is there no NET FORCE? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

25. ANALYZE: What will happen if there is no FRICTION? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT ball ball ball What will happen if there is no FORCE OF GRAVITY? What will happen if there is no SUPPORT FORCE?

26. ANALYZE: Are the forces FRICTION and FORCE OF GRAVITY balanced? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT ball ball ball What do you think is this SUPPORT FORCE called?

27. T he friction between the jar and the ball and the force of the earth on the ball ( Gravitational force ) would balance out each other, otherwise the ball will drop. Nothing will balance the support force of the glass on the ball so it would be the NET FORCE on the ball. Since there is a Net Force on the ball, what will happen to it? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT ball ball ball

28. The object is accelerating because it’s changing its direction of motion in every point in the circular path while maintaining its constant speed (noting that the object travels the same distance because the radius of the circular path is not changing). DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT ball ball ball

29. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT Based on the Activity : Does the ball undergo Uniform Circular Motion? Why?

30. UNIFORM CIRCULAR MOTION a type of motion of an object in a circular path with a constant speed but changing direction due to a net force. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

31. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT Compare centripetal force and centripetal acceleration.

32. I n uniform circular motion, the direction of the velocity changes every point along the circular path . This change in direction is an indication that the object is accelerating, and the direction of acceleration is towards the center of the circular path – thus it is called as Centripetal Acceleration. Following Newton’s Second Law, centripetal acceleration is caused by a NET FORCE – the Centripetal Force. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

33. “Wall of Death” DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

34. Draw the possible forces that will act on the motorcycle and the rider while moving along the “Wall of Death”. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

35. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

36. Let’s view the “Wall of Death” from the top. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

37. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT Let’s view the “Wall of Death” from the top.

38. Think W hat will happen to the motion of an object moving in circular motion when the centripetal force “suddenly disappears”? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

39. Activity: “Whirl and Release” - perform again the ball and jar challenge but this time on the top of the table. Let the ball whirl around the jar. Then, suddenly release the ball by lifting the jar. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

40. Activity: What have you observed when the ball was released? How can you describe the path of the ball? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

41. Which path in the figure at right would the ball most closely follow after it exits the channel at "r" and moves across the frictionless table top? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

42. Which path in the figure at right would the ball most closely follow after it exits the channel at "r" and moves across the frictionless table top? Answer: B DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

43. At point A, the velocity vector of a body moving in a circular motion is directed TANGENT to the circular path. Hence the term TANGENTIAL VELOCITY . DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

44. In the event that the centripetal force “suddenly disappears”, there will be no net force that would make the object accelerate, and so due to the object’s inertia , it will continue to move in a straight path, tangent to the original circular path. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

45. A steel ball is attached to a string and is swung in a circular path in a horizontal plane as illustrated in the accompanying figure on the left. At the point P indicated in the figure, the string suddenly breaks near the ball. If these events are observed from directly above as in the figure, which path would the ball most closely follow after the string breaks? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

46. A steel ball is attached to a string and is swung in a circular path in a horizontal plane as illustrated in the accompanying figure on the left. At the point P indicated in the figure, the string suddenly breaks near the ball. If these events are observed from directly above as in the figure, which path would the ball most closely follow after the string breaks ? ANSWER : B DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

47. Are you familiar with the Hammer Throw? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT http://media.almasryalyoum.com/News/Large//2012/08/03/228/2012-08-03t115018z_1015843940_lm2e8830wvnxg_rtrmadp_3_oly-athl-atmham-atm054901.jpg

48. What if Thor really do the Hammer throw? https://s-media-cache-ak0.pinimg.com/736x/e5/6b/a6/e56ba6c90f838fc00b818db4dda52f7d--hammer-throw-thors-hammer.jpg

49. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT The velocity of an object moving in UCM is Tangent to the circular path The Centripetal force and Centripetal acceleration are both directed radially inward, towards the center of the circular path

50. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT Thor is participating in an Olympic game of Hammer Throw (Literally!). He aims to throw his hammer with the fastest speed as possible .

51. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT Tony Stark (Iron Man) wishes to challenge Thor and test his Physics competence and he suggested that Thor should attach a chain on the hammer so as to make it swirl with a larger circumference and thereby producing faster speed in throwing the hammer. Is the suggestion helpful for Thor? http://68.media.tumblr.com/1eccbad7250ac453997a617aaf1e0a9a/tumblr_n75kpgSqMw1spgj0xo7_1280.png  

52. Activity: Round and Around We Go Investigate the factors affecting the speed (magnitude of the velocity) of an object moving in circular motion. Use the provided materials and follow the procedures in the Activity Sheets provided. Write your data in a Manila Paper to be presented after the activity. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

53. Activity Proper “ ROUND AND AROUND WE GO ” DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

54. Part 1 1. Is the distance covered by the stopper changing? What made you say so ? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

55. Part 1 1. Is the distance covered by the stopper changing? What made you say so? The distance covered is the same all throughout. The length of the string is kept approximately constant. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

56. Part 1 2 . What does the time to complete 20 revolutions represent? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

57. Part 1 2 . What does the time to complete 20 revolutions represent? The time to complete 20 revolutions would represent how fast the stopper is moving. Greater time for 20 revolutions indicate slower motion while lesser time for 20 revolutions represent faster motion . DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

58. Part 1 3. What does the number of washers or candies hanging represent ? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

59. Part 1 3. What does the number of washers or candies hanging represent? The number of washers or candies represent the force exerted by the string on the stopper – the tension force on the stopper. It is directed towards the center of the circular path along the string therefore it is considered to be a centripetal force . DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

60. Part 1 4 . What happens to the time of revolution as the number of washers / candies is increased? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

61. Part 1 4 . What happens to the time of revolution as the number of washers / candies is increased? The time to complete 20 revolutions decreases as more washers/candies are attached to the set up. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

62. Part 1 5. What relationship exists between the speed/velocity and the centripetal force of an object moving in Uniform Circular Motion? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

63. Part 1 5. What relationship exists between the speed/velocity and the centripetal force of an object moving in Uniform Circular Motion? The centripetal force and the speed / velocity of an object moving in Uniform Circular Motion are directly proportional to each other. As the centripetal force is increased, the speed/velocity of the moving body also increases (becomes faster) DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

64. Part 2 1. Is the distance covered by the stopper changing? What made you say so? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

65. Part 2 1. Is the distance covered by the stopper changing? What made you say so? Yes the distance covered by the stopper is changing. The length of the string has changed where the stopper is attached is changed . DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

66. Part 2 2 . What does the time to complete 20 revolutions represent? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

67. Part 2 2 . What does the time to complete 20 revolutions represent? The time to complete 20 revolutions would represent how fast the stopper is moving. Greater time elapsed for 20 revolutions indicate slower motion while lesser time for 20 revolutions represent faster motion. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

68. Part 2 3. What happens to the time of revolution as the length of the string attached to the stopper is increased? What does this indicate about the speed of the stopper moving in Uniform Circular Motion? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

69. Part 2 3. What happens to the time of revolution as the length of the string attached to the stopper is increased? What does this indicate about the speed of the stopper moving in Uniform Circular Motion? The time to complete 20 revolutions becomes larger/longer as the length of the string attached to the stopper is increased. This indicates that the speed of the object moving in Uniform Circular object decreases (becomes slower) DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

70. Part 2 4. What relationship exists between the speed/velocity and the radius of the path of the object moving in Uniform Circular Motion? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

71. Part 2 4. What relationship exists between the speed/velocity and the radius of the path of the object moving in Uniform Circular Motion? The speed/magnitude of the velocity of the moving object is inversely proportional to the radius of the circular path. As the radius of the circular path increases, the time to complete a revolution becomes larger, thus making the speed slower. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

72. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT Tony Stark (Iron Man) wishes to challenge Thor and test his Physics competence and he suggested that Thor should attach a chain on the hammer so as to make it swirl with a larger circumference and thereby producing faster speed in throwing the hammer. Is the suggestion helpful for Thor? http://68.media.tumblr.com/1eccbad7250ac453997a617aaf1e0a9a/tumblr_n75kpgSqMw1spgj0xo7_1280.png  

73. Tony Stark’s suggestion is wrong! If a chain is attached to Thor’s hammer, it would make the radius of the circular path of the whirled hammer larger, thus the speed of the hammer’s revolution would be slower . DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

74. As a group, use meta-cards to make an Eight-word Memoir: Using only eight words, form a sentence which summarizes the important concepts learned in the lesson. DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

75. Summing it up: What lessons have you learned in Uniform Circular Motion? DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

76. Check Up. PLICKER CARDS. Each group will be given Plicker cards. These Plicker cards will be used in answering the given check-up questions. Each group will raise their cards with their answers and the facilitator will scan the them using mobile phone. After all the cards were scanned, the facilitator will announce which group got the correct answer.

77. Check Up: In a Circular Motion, what happens to the distance travelled by the object when the radius of the path is increased ? The distance travelled is increased The distance travelled is decreased The distance travelled remains the same DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

78. Check Up: In a Circular Motion, what happens to the distance travelled by the object when the radius of the path is increased ? The distance travelled is increased The distance travelled is decreased The distance travelled remains the same DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

79. Check Up: 2. In Circular Motion, what happens to the TIME to complete the motion when the RADIUS of the circular path is increased ? The time to complete the motion is increased The time to complete the motion is decreased The time to complete the motion remains the same DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

80. Check Up: 2. In Circular Motion, what happens to the TIME to complete the motion when the RADIUS of the circular path is increased ? The time to complete the motion is increased The time to complete the motion is decreased The time to complete the motion remains the same DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

81. Check Up: 3. In Circular Motion, what happens to the speed/magnitude of velocity when the radius of the circular path is increased ? The speed / magnitude of the velocity increases The speed / magnitude of the velocity decreases The speed / magnitude of the velocity remains the same The speed / magnitude of the velocity becomes zero DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

82. Check Up: 3. In Circular Motion, what happens to the speed/magnitude of velocity when the radius of the circular path is increased ? The speed / magnitude of the velocity increases The speed / magnitude of the velocity decreases The speed / magnitude of the velocity remains the same The speed / magnitude of the velocity becomes zero DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

83. Thank you very much! DEPARTMENT OF EDUCATION – BUREAU OF CURRICULUM DEVELOPMENT

84. DLP Writing Session 3: Uniform Circular Motion [email protected]