Describing Motion

• Scalar quantity


  • A quantity that only has a magnitude
  • A quantity that isn't direction dependent
• Vector quantity


  A quantity that has both a magnitude and an associated direction
• How vector quantities are represented


  • Using vector arrows
  • The length of the arrow represents the magnitude
  • The arrow points in the associated direction
• Vector quantities


  • Velocity
  • Displacement
  • Force
• Velocity


  The speed of an object in a specific direction
• Gradient of distance/time graph


  The speed
• Gradient of displacement/time graph

  The velocity
• Calculating speed at a given time from a distance-time graph for an accelerating object


  1. Draw a tangent to the curve at the required time

  2. Calculate the gradient of the tangent
• Calculating distance travelled from a velocity-time graph


  It is equal to the area under the graph
• Gradient of velocity/time graph

  The acceleration
• Typical value for the speed of sound
• Typical value for human walking speed 1.5 m/s
• Typical value for human running speed 3 m/s
• Typical value for human cycling speed 6 m/s
• Approximate value for the acceleration of an object in free fall under gravity near the Earth's surface