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L3 L3 Presentation Transcript

  • Physics L3 www.slideshare.net/DMS_physics
  • Free Fall
    • … occurs if the only force on an object is gravity.
    • Acceleration of gravity
    For convenience we can use g = 10 m/s 2
  • How Fast ? 10t t . . . . 50 5 40 4 30 3 20 2 10 1 0 0 Instantaneous Speed (m/s) Elapsed Time (s)
  • How Fast ?
  • Question
    • What would the speed of the apple be
      • after 4.5s?
      • after 8s?
      • after 15s?
    10t t . . . . 50 5 40 4 30 3 20 2 10 1 0 0 Instantaneous Speed (m/s ) Elapsed Time (s)
  • Speed Graph
    • In Uniform Motion
      • speed is directly proportional to time
      • The graph is a straight line
      • The slope is acceleration
  • Question
    • What would the speed of the apple be
      • after 4.5s?
      • after 8s?
      • after 15s?
    • 45 m/s
    • 80 m/s
    • 150 m/s
    • Acceleration is 10m/s 2 downwards at all times
    • At the same height
      • Speeds are the same
      • Velocities are in the opposite directions
    t = 3s, v = 0m/s t = 2s t = 1s t = 0s t = 4s t = 5s t= 6s t = 7s v = 20m/s v = 10m/s v = 30m/s v = 40m/s
  • t = 3s, v = 0m/s t = 2s t = 1s t = 0s t = 4s t = 5s t= 6s t = 7s v = 20m/s v = 10m/s v = 30m/s v = 40m/s
  • t = 3s, v = 0m/s t = 2s t = 1s t = 0s t = 4s t = 5s t= 6s t = 7s v = 20m/s v = 10m/s v = 30m/s v = 40m/s
  • Average Speed
    • For objects moving with constant acceleration , the average speed is the arithmetic mean (average) of the initial and final speeds.
    10t t . . . . 50 5 40 4 30 3 20 2 10 1 0 0 Instantaneous Speed (m/s ) Elapsed Time (s)
  • How far ?
  • How far ? 5t 2 t . . . . 125 5 80 4 45 3 20 2 5 1 0 0 Distance (m) Elapsed Time (s)
  • Classwork (p.20/Q)
    • An apple falls from a tree and hits the ground in one second.
      • What is its speed upon striking the ground?
      • What is its average speed during this 1s?
      • How high above the ground was the apple when it was dropped?
  •  
  • Homework Assignment
    • P.26 / 16,17,19
      • For a freely falling object dropped from rest, what is the
        • Instantaneous speed at the end of the fifth second of fall?
        • Acceleration at the end of the fifth second of fall?
        • Distance covered by the end of the fifth second of fall?
  • End L3 www.slideshare.net/DMS_physics