# 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
Combining Displacements
Non-Straight Line
• For a non-straight line
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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 views: 8 posted: 3/11/2012 language: pages: 10