moments

• what's the average walking speed?

  1.5m/s
• what's the average running speed?

  3m/s
• what's the average cycling speed?

  6m/s
• What happens to a parachutist during terminal velocity

  1. At the start of the jump, air resistance is zero so they accelerate downwards due to gravity

  2. As speed increases, air resistance increases

  3. Eventually air resistance equals weight, forces are balanced, speed becomes constant (terminal velocity)

  4. When parachute opens, air resistance suddenly increases, resultant force is upward causing deceleration

  5. As they slow down, air resistance decreases until it balances their weight, reaching a new lower terminal velocity
• Moment


  Alternative name for the turning effect of a force
• If an object is in equilibrium, the clockwise moments are equal to the anticlockwise moments
• Parts of a lever system


  • Load
  • Effort
  • Pivot
• How a lever can be used as a force multiplier

  • If the distance between the effort and pivot is greater than the distance between the pivot and load, the force applied on the load is greater than the effort force. This is since the moment on both the effort and load must be the same.
• Example of when a lever may be used to multiply a force

  • A wrench, which has a long handle so that the force applied by the user is multiplied
• What determines the moment of a gear wheel

  The size of the wheel
• A larger gear being driven by a smaller gear will rotate more slowly but will also produce a larger moment