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Physics 10

Physics 10. MONDAY APRIL 14 th physics behind the knuckleball Physics PRE-ASSESSMENT Complete the true or false on page 1 of your Home Work Book 8 questions… do your best we will go over the answers. True or False. 1) F, scalar quantities have only magnitude 2) T

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Physics 10

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  1. Physics 10 • MONDAY APRIL 14th • physics behind the knuckleball • Physics PRE-ASSESSMENT • Complete the true or false on page 1 of your Home Work Book • 8 questions… do your best we will go over the answers. (c) McGraw Hill Ryerson 2007

  2. True or False • 1) F, scalar quantities have only magnitude • 2) T • 3) F , If a trip takes you back to where you started, your displacement is zero. • 4) F, distance is always greater or equal to the displacement • 5) T • 6) F, A straight horizontal line on a position time graph indicates the object is not moving. • 7)F, The speed of an object is always greater than or equal to the magnitude of its velocity. • 8) F , To calculate the acceleration of an object , you need to know both velocity and time. (c) McGraw Hill Ryerson 2007

  3. 8.1 The Language of Motion • Many words are used when describing motion. • Many of these words have specific meanings in science. • Some common words used to describe motion include: • Distance • Time • Speed • Position Describe the motion of the soccer ball before and after it is kicked. What key words did you use when describing this situation? See pages 344 - 345 (c) McGraw Hill Ryerson 2007

  4. Kinematics • All sports are a combination of athletic skill and science. • In physics, the study of an object’s motion in terms of its change in position, velocity, and rate of change in velocity is called kinematics (derived from Greek – motion). • Kinesiology: the study of human body movement. (c) McGraw Hill Ryerson 2007

  5. Direction Makes a Difference • Quantities that are measured or counted have a magnitude but may also contain a direction. • Magnitude refers to the size of a measurement or the amount you are counting. • Magnitude is simply the “size” of a quantity. • Magnitudes are expressed in numerical form e.g., 450, 0.45,2/3 etc. • Quantities that describe magnitude but give no direction, are distance, time and speed. (c) McGraw Hill Ryerson 2007

  6. Scalar • Quantities that describe magnitude but do not include direction are called scalar quantities or scalars. • Example: 25 seconds • A common example of a scalar quantity is speed. • Example: If a man is driving at a speed of 50km/h, we say the magnitude of the scalar quantity is 50. • Notice that the sentence “I am driving 50” is incomplete. Therefore, the magnitude is equipped with a unit, in this case km/h. (c) McGraw Hill Ryerson 2007

  7. Vectors • Quantities that describe magnitude and also include direction are called vector quantities or vectors. • Example: 5 km north • Video clip Every time you use a map or give directions, you are using vectors. (c) McGraw Hill Ryerson 2007

  8. Question • Question: What is the quantity that describes the length of a path between two points or locations? (c) McGraw Hill Ryerson 2007

  9. Distance • Distance (d) is a scalar quantity that describes the length of a path between two points or locations. • Example: Olaf ran a distance of 400 m to reach his head. Olaf (c) McGraw Hill Ryerson 2007

  10. Question • Question: What is the quantity that describes a specific point relative to a reference point? (c) McGraw Hill Ryerson 2007

  11. Position • Position ( ) is a vector quantity that describes a specific point relative to a reference point. • Example: Sven galloped 1km east across the ice to reach Olaf’s carrot nose. See pages 346 - 347 (c) McGraw Hill Ryerson 2007

  12. Distance verses Position • A car leaves home and drives 10 km to the store and then returns home. The car has driven a total distance of 20 km but its final displacement is 0 km. • You drove to the store from your house. Describe the location of your car in relation to your house. • Your distance driving to the store and back is _________? • Your position upon returning home if ________? The cars position is 10km east. 20km 0km (c) McGraw Hill Ryerson 2007

  13. Vector vs. Scalar • You can always tell if a quantity is a vector because there will be an arrow drawn above it. • Example: • A scalar has no arrow. • Example: The SI unit for both distance and position is metres, m. (c) McGraw Hill Ryerson 2007

  14. SI Unit • The SI unit for both distance and position is metres, m. (c) McGraw Hill Ryerson 2007

  15. Summary so far • Scalar • Distance - d • SI unit: metres • Vector • Position - • SI unit: metres (c) McGraw Hill Ryerson 2007

  16. Time • Time (t) is a concept that describes when an event occurs. • Initial time (ti) is when the event began. • Final time (tf) is when the event finished. • Example: The birthday party starts at 3pm. • 3pm is the initial time for the party • The party was over at 6pm. (c) McGraw Hill Ryerson 2007

  17. Question • Question: What is the term used for the difference between the final and the initial time? (c) McGraw Hill Ryerson 2007

  18. Time Interval Time interval is the difference between the final and initial times. Time interval is calculated by: • The symbol for a change in time or time interval is ∆t See page 348 (c) McGraw Hill Ryerson 2007

  19. Time interval example The position of the sign is 7 m east of the tree. • The time interval to move from the fire hydrant to the sign is calculated by: (c) McGraw Hill Ryerson 2007

  20. SI Unit • The SI unit for time and time interval is seconds, s. (c) McGraw Hill Ryerson 2007

  21. Question: You leave your class (t=0s) and walk to your car 50 m away (ti = 60s) and drive to Dairy Queen, have a chocolate cherry blizzard and return to school (tf = 2100s). What is your time interval? • ∆t = tf - ti = 2100s – 60s = 2040 s • What is your position? Lets find out! (c) McGraw Hill Ryerson 2007

  22. Displacement and Distance • Displacement describes the straight-line distance and direction from one point to another. • Displacement describes how much an object’s position has changed. • If the object ends up back where it started, its displacement is • Example: Your displacement from 0km to Dairy Queen and back is Zero See page 349 (c) McGraw Hill Ryerson 2007

  23. Displacement • Displacement is equal to the final position minus the initial position. • The SI unit for displacement is metres, m. (c) McGraw Hill Ryerson 2007

  24. Question: For the skateboarder, in the time interval from 2 s to 5 s, the displacement is? • The skateboarder’s distance travelled is? 5 m [E] (c) McGraw Hill Ryerson 2007

  25. Vector vs Scalar • Since, it includes direction, displacement is a vector quantity. • The symbol for displacement is ∆d (c) McGraw Hill Ryerson 2007

  26. Summary so far • Scalar • Distance - d • SI unit: metres • Time – t • SI unit - s • Vector • Position - • SI unit: metres • Displacement – • SI unit – metres (m) ﺤ ∆d (c) McGraw Hill Ryerson 2007

  27. Watch for Signs When using vector quantities, opposite directions are given opposite signs. Common sign conventions See page 349 (c) McGraw Hill Ryerson 2007

  28. Example • Between 0 s and 15 s the person’s displacement is What distance did the person walk in this same time interval? = 10 m [W] – 5 m [E] = -10 m – 5 m = -15 m = 15 m [W] 45 s (c) McGraw Hill Ryerson 2007

  29. Question • Is it a vector or scalar? • Distance • 35 km [E] • Time interval • position (c) McGraw Hill Ryerson 2007

  30. Question • Explain what would be more useful to you if you needed to locate the shrink ray from “Vector”: the distance to the shrink ray or the position of the shrink ray? • Answer: The position would be more useful since position includes not only the distance the shrink ray is from the starting point but also the direction. (c) McGraw Hill Ryerson 2007

  31. Complete ∆t Second ∆d Metre m Position (c) McGraw Hill Ryerson 2007

  32. The End • Oh Yeah! (c) McGraw Hill Ryerson 2007

  33. Activity • With a partner get a lap top and complete the “graphing motion computer lab” assignment. • What ever you don’t finish in class is Home Work. (c) McGraw Hill Ryerson 2007

  34. Motion: 8.1 • TUESDAY APRIL 15th Pre-assess Do Questions Four on page 4 of 8.1 notes package. Graph the Data…. (c) McGraw Hill Ryerson 2007

  35. Questions Four Is the Object in Uniform Motion? NO, because the object travels different distances during different intervals of time. (c) McGraw Hill Ryerson 2007

  36. Uniform Motion • Objects in uniform motion travel equal displacements in equal time intervals. • Objects in uniform motion do not speed up, slow down, or change direction. See page 350 (c) McGraw Hill Ryerson 2007

  37. Uniform motion The position of Wile E. Coyote in this photo is shown at equal time intervals. How would you determine if this motion is uniform motion? (c) McGraw Hill Ryerson 2007

  38. Uniform Motion • You can represent the motion of an object in a variety of ways. • One way is: Wile E Coyote can be represented by a motion diagram. (c) McGraw Hill Ryerson 2007

  39. Motion Diagram t=5 s t=0 s t= 1 s t=3 s t=4 s t= 2 s 0 cm 80 cm 100 cm 20 cm 40 cm 60 cm • A motion diagram shows the objects position at given times and allows us to picture or visualize motion. (c) McGraw Hill Ryerson 2007

  40. Graphing Uniform Motion • Motion of an object can be analyzed by drawing a position-time graph. See page 351 (c) McGraw Hill Ryerson 2007

  41. The motion diagram allowed us to identify Wile E Coyote at corresponding time intervals. • The data can be used to make the position-time graph. Table: Position of Wile E Coyote (c) McGraw Hill Ryerson 2007

  42. Graphing Uniform Motion • A position-time graph plots position data on the vertical axis (y axis) and time data on the horizontal axis (x axis). (c) McGraw Hill Ryerson 2007

  43. Uniform motion • A straight line passing through the plotted data indicates uniform motion. • The straight line passes through all the plotted points. (c) McGraw Hill Ryerson 2007

  44. Question? • What is a best-fit line? (c) McGraw Hill Ryerson 2007

  45. Best-fit Line • Real motion is not perfectly uniform. • ie. Measuring errors • A best-fit line is a smooth curve or straight line that most closely fits the general shape outlined by the points. (c) McGraw Hill Ryerson 2007

  46. The best-fit line allows you to find the position of Wile E. Coyote at any given time. • The motion diagram only provides Wile E Coyote’s position at 5 separate times. (c) McGraw Hill Ryerson 2007

  47. Example of best-fit. • Question: Find the position of Wile E. Coyote at 3.5 s (c) McGraw Hill Ryerson 2007

  48. Best-fit line • FYI: A best-fit line can also be extended beyond the first and last points to indicate what might happen beyond the measured data. (c) McGraw Hill Ryerson 2007

  49. Slope • The slope of a graph refers to whether a line is horizontal or goes up or down at an angle. Question: What are the different types of slope? See pages 353 - 354 Take the Section 8.1 Quiz (c) McGraw Hill Ryerson 2007

  50. Positive slope • Positive slope • Slants up to the right • Indicates motion in the direction of the positive y axis (c) McGraw Hill Ryerson 2007

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