Moments, levers and gears

• Moment

  The turning effect of a force
• Moment force

  Force x Distance (Perpendicular to)
• Pivot


  A point which something can turn around
• Lever


  A bar or rod pivoted at a fixed hinge
• Parts of a lever

  • Effort
  • Pivot
  • Load
• Mechanical advantage

  Less force is required to move the load
• The longer the lever and further the effort acts from the pivot, the easier it is to move the load
• Gears


  • Can be used to increase/decrease the rotational speed and torque of a mechanical system
• Input gear

  The gear that is being turned by an external force
• Output gear

  The gear that is turning the system
• Torque


  A measure of the force that can cause an object to rotate about an axis
• Rotational speed


  The number of rotations an object makes in a given time
• Rotational inertia

  The resistance of an object to changes in its rotation
• Friction

  The force that resists the motion of one surface relative to another
• Principle of Moments


  When a system is balanced, the sum of the anticlockwise moments equals the sum of the clockwise moments about a pivot
• Moments are measured in newton-meters (Nm)