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Acceleration

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					 ACCELERATION
         Key Concepts

•What kind of motion does
acceleration refer to?
•How is acceleration calculated?
•What graphs can be used to
analyze the motion of an
accelerating object?
Key Terms

 Acceleration
What is Acceleration?

 Everyday language – the process of speeding
  up
 Scientific definition – the rate at which
  velocity changes
 A change in velocity can be a change in speed
  or direction – or both
 Therefore acceleration refers to increasing
  speed, decreasing speed or changing
  directions
Increasing Speed

Examples:
 A car moving from a stopped position
 A car speeding up to pass another car
 A person coasting down a hill on a bicycle
  Decreasing Speed
  Negative acceleration
Examples
 Softball landing in fielder’s mitt
 A car stopping at a red light
 Water skier when the boat stops pulling
Changing
Direction
Examples
 A car following a bend in the road at constant
  speed
 A car changing lanes on a highway
 A softball as it changes directions when it is
  hit
 Circular motion such as a Ferris wheel is
  continuous acceleration although the speed
  may not change
Calculating Acceleration

 If an object is not changing direction you can
  calculate its acceleration as the rate at which
  its speed changes
Formula:
 Acceleration = Final speed – initial speed
                        Time
Units for Acceleration

If speed is measured in meters/second and time
   is measured in seconds, the SI unit for
   acceleration is m/s/s or m/s2

If speed is measured in km/hr and time is
   measured in hrs, the SI unit for acceleration is
   km/hr/hr or km/hr2
Acceleration Example

 Look at the plane on p. 24 and 25
 The plane’s initial speed is 0m/s
 The plane’s final speed is 40 m/s
 The time it took for the plane to speed up to
  40m/s was 5 s.
 Acceleration = final speed – initial speed
                          Time
=40m/s-0m/s =40m/s =8m/s2
      5s         5s
Graphing Acceleration

 speed vs time graphs and distance vs time
  graphs can be used to analyze the motion of
  an accelerating object
Speed vs Time Graphs

 Upward slanting line shows that speed is
  increasing
 Downward slanting line shows that speed is
  decreasing
 Straight line shows that acceleration is
  constant
 Find acceleration by calculating the slope of
  the line – slope = Rise
                   Run
Speed vs Time Graph
Distance vs Time Graph

 Represents the motion of an accelerating
  object
 Curved line means an object is accelerating
 Shows that during each second the object
  travels a further distance
 Also shows that each second the speed is
  greater than the second before
Distance vs Time graph
Distance vs time graph

				
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posted:5/2/2013
language:English
pages:15