Forces and Motion

• Scalar quantity


  Has only magnitude
• Vector quantity


  Has magnitude and direction
• Distance


  A scalar quantity
• Displacement


  A vector quantity
• Typical values for speeds

  • Walking speed - 1.5 m/s
  • Running speed - 3 m/s
  • Cycling speed - 6 m/s
• Speed of sound is 330 m/s
• Speed equation


  Speed = distance / time
• Speed


  The rate of change of position of an object
• Velocity


  The speed of an object in a given direction
• Calculating speed from a distance-time graph

  The speed of an object can be calculated from the gradient of a distance-time graph
• Calculating acceleration from a velocity-time graph

  The acceleration can be calculated from the gradient of a velocity-time graph
• Acceleration


  Change in velocity of an object per second, m/s²
• Calculating distance from a velocity-time graph

  The distance travelled can be calculated from the area under a velocity-time graph
• Symbols in the equation v = u + at

  • v - final velocity (m/s)
  • u - initial velocity (m/s)
  • a - acceleration (m/s²)
  • s - distance travelled (m)
• As an object travels faster


  The air resistance increases
• Gravitational field strength has units of m/s²
• Terminal velocity


  The constant velocity a falling object reaches when the resistive force is equal to its weight
• The drag on an object always acts in the opposite direction to its motion