Distance, Displacement, Speed and Velocity

• Distance


  How far an object has moved, a scalar quantity
• Displacement


  The distance and direction in a straight line from an object's starting point to its finishing point, a vector quantity
• Walking 5 m north, then 5 m south

  Displacement is 0 m, but distance travelled is 10 m
• Speed


  How fast you're going, a scalar quantity
• Velocity


  Speed in a given direction, a vector quantity
• Object moving in a circle at constant speed


  Velocity is constantly changing
• Measuring speed of an object with constant speed


  1. Time how long it takes to travel a certain distance

  2. Calculate speed using formula: distance = speed x time
• Objects rarely travel at constant speed
• Typical everyday speeds


  • Person walking - 1.5 m/s
  • Person running - 3 m/s
  • Person cycling - 6 m/s
  • Car - 25 m/s
  • Train - 55 m/s
  • Plane - 250 m/s
• Speed of sound (330 m/s in air) changes depending on what the sound waves are travelling through
• Wind speed is affected by temperature, atmospheric pressure, and nearby structures
• Speed equals distance divided by time