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					Relative Motion
   Chapter 3 Section 4
           Frames of Reference
-   If your in a car going down the road at
    60mi/hr due north and a car passes you
    going 70mi/hr due north, it seems as if the
    car passing you is going 10mi/hr.
-   Someone standing on the side of the road
    would view the faster car going 70mi/hr,
    not the 10mi/hr which you see it as.
         Frames of Reference
► Ifyou are riding your bicycle along the road
  at 10mi/hr due east and another bicycle
  passes you going 15 mi/hr due west, it
  looks as if the faster moving bicycle is going
► To someone standing along the road, it
  looks as if the bicycle is only going 15 mi/hr.
          Frames of Reference
► The examples are good explanations of how
 velocities change when viewed in different
 reference frames.

► Frame of Reference: The motion of an
 object is determined by the reference point
 of the observer and can change from one
 point to the next.
           Relative Velocity
► There is no general equation used to
 determine the relative velocity of an object
 given different reference points, but vector
 addition is used to solve most problems
 dealing with relative velocity.
     Relative Velocity Example
►A  boat heading north crosses a wide river
  with a velocity of 10.00 km/hr relative to
  the water. The river has a uniform velocity
  of 5.00 km/hr due east. Determine the
  velocity with respect to an observer on
► Pg 108
   sample problem 3F
             Practice Problems
1.   A passenger at the rear of a train traveling
     at 15m/s relative to earth throws a
     baseball with a speed of 15m/s in the
     direction opposite the motion of the train.
     What is the velocity of the baseball relative
     to earth as it leaves the thrower’s hand?
2. A spy runs from the front to the back of an
  aircraft carrier as a speed of 3.5m/s. If the
  aircraft carrier is moving forward at 18m/s,
  how fast does the spy appear to be running
  when viewed by an observer on a near by
3. A ferry is crossing a river. If the ferry is
  heading due north with a speed 2.5m/s
  relative to the water and the river’s velocity
  is 3.0m/s to the east, what will the boat’s
  velocity be relative to Earth?
4. A pet-store supply truck moves at 25m/s
  north along a highway. Inside, a dog
  moves at 1.75m/s at an angle of 35º east of
  north. What is the velocity of the dog
  relative to the road?

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