Distance and Displacement

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Distance and Displacement
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Scalar quantities

• Have magnitude (size) but no direction.
• Examples distance (10m)
• time (6 s)
• speed (12.3 km/h)

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Vector quantities

• Have both magnitude (size) and direction.
• Examples position (12 km due south)
• displacement ( 3m upward)
• velocity ( 13.5 m/s
  downward)

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Position

• Location of the object at a specific time
• displacement Positionfinal - Positioninital

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Example A physics teacher walks 4 meters East,
2 meters South, 4 meters West, and finally 2
meters North.

• Even though the physics teacher has walked a
  total distance of 12 meters, her displacement is
  0 meters.
• During the course of her motion, she has "covered
  12 meters of ground" (distance 12 m).
• Yet, when she is finished walking, she is not
  "out of place" i.e., there is no displacement
  for her motion (displacement 0 m).
  Displacement, being a vector quantity, must give
  attention to direction.
• The 4 meters east is canceled by the 4 meters
  west and the 2 meters south is canceled by the 2
  meters north.

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Example

• Tommy walks from home (0m) to school which is
  4.55 m North of his house. What is his
  displacement?
• ?d df di
• 4.55m 0m
• 4.55 m N or 4.55m

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Example

• A dog escapes from his owners house and finds a
  garden to dig up 21 m east of his house. He is
  scared off by a cat and ends up under a tree 6.5
  m east of his house. What is his displacement?
• ?d df di
• 6.5 m 21m
• -14.5 m (or 14.5 m west)

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Some examples of vector addition.