moments

• moment

  • turning effect of force around fixed point
• door example

  • doors open more easily if we exert force far away from the hinge, rather than next to it
  • pushing from further away increases the moment
• see-saw example

  • to balance the weight of a heavier person, a light person must sit further away from the pivot
• wrench example

  • when a mechanic uses a long wrench to tighten or loosen bolts, they’ll always hold it from the furthest end from the bolt
  • this magnifies force of their hand on the wrench
• for an object to be in equilibrium in linear motion:

  • must be no resultant force acting on the object
  • must be stationary or travelling at a constant speed in a straight line
• for an object to be in equilibrium in circular motion:

  • sum of clockwise moments must be equal to sum of anti-clockwise moments acting on object
  • means the object isn’t rotating at a constant speed
• principle of moments:

  • for an object to be in equilibrium, sum of all clockwise moments about a pivot point must be the same as the sum of all the anti-clockwise moments about pivot point