Motion and quantities

• Acceleration in SUVAT must be

  Acceleration must be uniform - if the acceleration is changing the equations wont be valid
• Gradient of a distance - time graph shows

  Speed
• Gradient of a displacement - time graph shows

  Velocity
• Gradient of a velocity - time graph shows

  Acceleration
• Uniform acceleration on a velocity time graph


  On a velocity time graph, if the acceleration is constant the gradient will be constant so it will form a straight line graph
• Non uniform acceleration on a velocity time graph

  If acceleration is not constant, the gradient will be changing so the graph will show a curve
• Velocity time graphs for a uniformly accelerating and a uniformly decelerating object

  • For an accelerating object the gradient will be positive
  • For a decelerating object the gradient will be negative
• Scalar quantity


  A scalar quantity is one that has a magnitude but not a fixed direction
• Vector quantity


  A vector quantity is one that has a magnitude and a fixed direction
• Five scalar quantities


  • Distance
  • Speed
  • Mass
  • Energy
  • Temperature
• Five vector examples


  • Displacement
  • Velocity
  • Acceleration
  • Momentum
  • Force
• Vector quantity on a diagram

  • As an arrow
  • The direction of the arrow represents the direction of the quantity
  • The length of the arrow represents the magnitude of the quantity
• Relationship between the perpendicular components of a vector


  The perpendicular components are independent of each other
• If a projectile is moving freely under gravity what is the vertical acceleration

  The vertical acceleration will be due to gravity and so will have a magnitude of 9.81ms^-1