Energy - forces and their effects

• gravitational attraction

  attraction between two objects with mass

  the large object gives a greater attraction
• electrostatic attraction/repulsion

  • larger charge gives greater force
  • like opposite charges attracting
• magnetic attraction/repulsion

  • stronger magnet gives stronger field, having a greater force
• normal contact force

  the force perpendicular to the plane of contact
• friction

  • surfaces that are rough cause friction when moved
• sky diver

  1. skydiver at the start has no air resistance and only weight
  2. he accelerates increasing speed - increasing air resistance
  3. acceleration decreases due to F = MA
  4. weight and air resistance are equal and balanced so there is no resultant force
  5. no acceleration = terminal velocity
• vehicle

  1. low air resistance and thrust is only slowed by friction
  2. air resistance increases decreasing resultant force
  3. car travels at terminal
  4. thrust is balanced by drag and friction
• rotation occurs

  • when an object is attached to a pivot point
  • force is applied perpendicular to the object
• M = FD

  Moment = force x distance
• what reduces friction

  lubricant
• gears

  change speed, force or direction by rotation
• if a gear with fewer teeth has force applied to it

  • second gear will turn faster
  • but with less force
  • and in the opposite direction to the first
• if a gear with more teeth has force applied to it

  • turns slower
  • more force
  • in the opposite direction to the first
• force

  push or pull in a particular direction
• thrust

  • caused by an engine
  • forward force
• upthrust

  • the force acts due to liquids
• tension

  • force on cables and strings
• free body diagram

  draw a dot and only resultant force
• parallelogram of forces

  1. draw to scale add force and angle
  2. draw parallelogram
  3. daw line in the middle
• moment

  turning force about a pivot
• balance

  total clockwise is equal to anti clockwise
• Principal of moments

  Total clockwise moment = to total anticlockwise moment