P9 - Motion

• Distance-time graphs


  • Shows how the distance travelled by an object travelling in a stright line changes with time
  • The gradient of the line is equal to the speed
• If an object is accelerating, the speed at any time can be found by calculating the gradient of a tangent to the curved line at that time on a distance-time graph
• Upwards curve on a distance-time graph


  accelerating
• Downwards curve on a distance-time graph


  reducing speed
• Steep, straight gradient on a distance-time graph


  high constant speed
• Horizontal line on a distance-time graph


  the object is stationary
• Acceleration


  • The change in velocity of an object per second
  • A vector
• Deceleration


  • Negative acceleration
  • Means an object is slowing down
• acceleration (m/s^2) = change in velocity (m/s) / time (s)
• Uniform acceleration


  when the acceleration of an object is constant
• Velocity-time graphs


  • shows how the velocity of an object changes with time
• Gradient of a velocity-time graph


  equal to the object's acceleration
• Area under a velocity-time graph


  equal to the distance travelled
• Straight line on a velocity-time graph


  constant acceleration
• Curved line on a velocity-time graph


  changing acceleration
• Horizontal line on a velocity-time graph


  constant velocity