Motion

• Distance


  Physical length between two objects, measured in metres (m)
• Speed


  Distance travelled per unit of time, e.g. m/s
• Velocity


  Speed in a particular direction, measured in m/s

  
• Equation for speed


  Speed = Distance / Time

  
• Distance-time graphs


  • Distance on y-axis, time on x-axis
  • Steeper line = faster
  • Horizontal line = stopped
  • Straight line = constant speed
  • Curved line = changing speed

  
• Newton's first law


  If resultant force is zero, stationary object remains stationary, moving object continues at same velocity

  
• Forces


  • Push or pull, measured in Newtons (N)
  • 1N is force to accelerate 1kg mass by 1m/s²
• Forces between objects


  • Equal and opposite forces
  • Floor pushes up on you as you push down
• Resultant force


  Effect of all forces combined
• Rules for calculating resultant force

  1. Forces in same direction add

  2. Forces in opposite directions subtract

  3. Vertical and horizontal forces considered separately

  
• Resultant force = 0 (balanced)


  Remains stationary or continues at constant speed
• Resultant force ≠ 0 (unbalanced)

  Acceleration, deceleration, change in direction

  
• Newton's second law


  Acceleration proportional to resultant force, inversely proportional to mass

  
• Acceleration


  • Change in speed over time, measured in m/s²
  • Acceleration = Change in speed / Time
  • Acceleration = (Final velocity - Initial velocity) / Time

  
• Stopping and braking distance

  • Affected by tiredness, alcohol, speed, road conditions, vehicle maintenance
  • Thinking distance + Braking distance = Stopping distance