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Free Fall and Graphs of Motion by liaoqinmei

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									 Free Fall
and Graphs
 of Motion
       A Falling Apple
 Consider   an apple falling
  from a tree
 It starts from a position of
  rest and gains speed as it
  falls.
 Gravity causes the apple to
  accelerate as it falls.
              Free Fall
 Describes  objects that are only
  affected by gravity.
 The speed of an object in free
  fall increases or decreases by
  9.81 m/s each second.
 9.81 m/s2 is the acceleration
  due to gravity.
 “g” represents the acc. due to
  gravity
          Straight Up
 Now    consider an object
  tossed straight up.
 As an object moves upward,
  it is accelerating (speed ).
  - the object slows at a rate of
  9.81 m/s2 (acc due to
  gravity).
       The highest point
 At its highest point, the
  object has an inst. speed of
  zero (b/c it has to stop to
  change directions)
 The object will fall as if it
  were dropped from its
  highest point.
         The way down
 As the object is falling, it will
  accelerate at 9.81m/s2
 The falling object will its
  speed by 9.81m/s each
  second.
        Height and Velocity
 The  inst. speed
  at points of
  equal
  elevations are
  the same.
 The velocities
  are different
  b/c they are in
  opposite
  directions.
  Air Resistance & Free Fall
 Causes   objects of different
  shapes to accelerate
  differently (stone vs feather)
 With negligible air resistance,
  falling objects can be
  considered freely falling.
The path is
symmetrical.
Acceleration is
constant.
The magnitude
of the velocities is
the same at equal
heights.
            Group Discussion
Two stones are thrown from a cliff at
the same time with the same speed,
one upward and one downward.
Which stone, if either, hits the ground
first? Which, if either, hits with the
higher speed?
    In a group discussion, make your
best argument for each possible
prediction. Set up numerical
examples and solve them to test your
prediction.

								
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