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Distance and Displacement - Piscataway Schools

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					Distance and Displacement

     Chapter 11 Section 1
           Key Concepts
• What is needed to describe motion
  completely?
• How are distance and displacement
  different?
• How do you add displacements?
               Vocabulary
•   Frame of reference
•   Relative motion
•   Distance
•   Vector
•   Resultant vector
                Review
• To describe motion accurately and
  completely, a frame of reference is
  necessary
• Frame of reference: system of objects
  that are not moving in respect to one
  another.
• Think back to our telescopes and cars!
       Measuring Distance
• Distance: the length of a path between
  two points
• SI units for distance: meter & kilometer
• Written as a number ( magnitude) with
  the unit
  – Example: I walked 4 km to my friend’s
    house
    Measuring Displacement
• Displacement: direction from the
  starting point and the length of a
  straight line from the starting point to
  the ending point
• Written with a number (magnitude),
  unit and direction
  – Example: I walked 4 km west to my
    friend’s house
     Combining Displacements
          Straight line
• For a straight line displacement: Add
  displacements using vector addition
         Combining Displacements
            Non-Straight Line
• For a non-straight line
  displacement: Add
  displacements using
  resultant vectors ( the
  red line on the picture)
• But how do I get the
  number for the red
  line?
      Pythagorean Theorem
If a = 3 & b= 4
Then c= ____
a2 +b2 = c2
32 + 42 = c2
9 + 16 = c2
C2 = 25
C= √ 25
C=5
             Triangle Hint
• 3-4-5 triangles. If using a right triangle
  and the Pythagorean theorem. If the
  legs of the triangle are multiples of 3
  and 4, the length of the longest side is
  going to be a multiple of 5

				
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