Scalars & Vectors

• Scalar quantity

  Described with a single number (with units) that gives its size or magnitude
• Scalar quantities


  • Temperature
  • Mass
• Vector quantity

  Has both magnitude and direction
• Vector quantities

  • Force
  • Displacement
• Vector quantity values

  • 10 m/s east
  • 500 N downward
• A vector quantity has a magnitude and a direction
• The colored arrow in the drawing represents a displacement vector
• Cartesian plane


  Coordinate system with x-axis (abscissa) and y-axis (ordinate)
• The origin is at (0,0)
• Speed


  Quantifies how fast or slow an object is
• Average speed


  Total distance / Total time
• Instantaneous speed


  Speed at a specific instant in time
• Speed = distance travelled / time to travel that distance
• Velocity


  Speed + direction
• Average velocity


  Displacement / Time
• Instantaneous velocity

  How fast an object moves and the direction of the motion at each instant of time