SP1, SP2, SP8, SP9

• Scalar Quantities


  have size but no direction, e.g. speed, distance, mass
• Vector Quantities


  have both size and direction e.g. velocity, force, weight and displacement
• Displacement


  How far you have travelled in a straight line from your starting point
• Momentum


  mass x velocity

  
• Difference between acceleration and velocity


  Acceleration= change in speed in given time

  Velocity= speed in a particular direction
• Distance


  speed x time

  
• Distance Graph tips


  Straight- travelling at constant speed

  Horizontal- stationary
• Acceleration


  Change in speed / time taken

  
• Acceleration 2nd formula


  (v)^2-(u)^2 = a x 2 x x

  x= distance
• Thrust or up-thrust


  thrust- makes object move forward

  up-thrust- pushes object up

  *free-body diagrams
• What forces do to an object?

  1. speed it up
  2. slow it down
  3. change direction
  4. change shape
• Newtons first law


  *law of inertia

  objects in motion tend to stay in motion with the same speed and direction unless acted upon by an unbalanced force
• Centripedal force


  resultant force that causes the object to move in a circular motion
• Weight

  mass x gravitational field strength

  *On earth it is 10

  
• Mass or weight


  mass- how much matter an object has in it

  weight- force of gravity on an object
• Force


  mass x acceleration
• Terminal velocity


  constant speed when the driving force is max
• Action-reaction forces


  -occur in pairs

  -same size but opposite direction

  -same type of force
• Balanced forces


  -same object

  -different force
• Newtons third law


  For every action force, there is a equal and opposite reaction force
• Momentum


  how difficult it is to stop a moving object
• Conservation of momentum


  total momentum before collision= total momentum after the collision
• Impact force


  change in momentum / time
• Reaction time


  time taken between detecting a stimulus and responding
• Factors affecting reaction + thinking distance

  1. alcohol
  2. age
  3. drugs
• thinking distance


  distance between seeing the hazard and hitting the brakes
• braking distance


  distance you travel between applying brakes and car stopping
• stopping distance


  thinking distance + braking distance
• Factors affecting braking distance

  1. friction
  2. heavy vehicle
  3. tyre conditions
• work done


  work done= useful energy transferred

  *measured in joules
• Kinetic energy

  1/2 x m x v^2

  
• work done


  force x distance moved
• work done = kinetic energy transferred
• What reduces injury in a crash?

  1. seatbelts
  2. crumple sone
  3. airbags
• gravitational potential energy


  mgh
• non-contact forces

  1. gravity
  2. magnetic
  3. electrostatic
• Contact forces

  1. thrust
  2. friction
  3. air/water resistance
• Principle of moments


  In equilibrium,sum of clockwise moments= sum of anti-clockwise moments
• Moment


  force x distance

  
• What are gears?


  -rotating wheel with teeth that interlock with another wheel

  -transmit rotational forces