springs, levers and gears

• forces don't just make objects move, they can also make them change...

  shape - whether they change shape temporarily or permanently depends on the object and the forces applied
• to stretch, compress or bend an object...

  there must be more than one force acting on the object, otherwise the object would simply move in the direction of the applied force instead of changing shape
• when a force stretches, compresses or bends an object...

  work is done and causes energy to be transferred to the elastic potential energy store of the object
• if an object is elastically deformed, ... the energy is transferred to the object's ...

  all, elastic potential store
• elastic deformation


  an object that has been elastically deformed if it can go back to its original shape and length after the force has been removed. these objects are called elastic objects
• Inelastic deformation


  an object has been inelastically deformed if it doesn't return to its original shape and length after the force has been removed
• extension is ... to force

  directly proportional
• Force (N) =


  spring contact (N/m) x extension (m)
• extension formula


  F=ke
• extension formula triangle

  
• there is a ... to the amount of force you can apply to an object for extension to keep on increasing proportionally

  limit
• limit proportionality


  the limit beyond which, when a wire or spring is stretched, its extension is no longer proportional to the force that stretches it - when the force is taken away, it will not return to its original length
• spring constant


  the measure of the stiffness of the spring
• Hooke's law


  the law stating that the stress of a solid is directly proportional to the strain applied to it (F=ke)
• a moment is ...

  the turning effect of a force
• moment of a force (Nm) =

  force (N) x perpendicular distance from the pivot (m)
• moment of force triangle

  
• moment of force formula

  M=Fd
• the force of the spanner causes a ... effect or moment on the nut

  turning
• to get maximum moment you need to push ... to the spanner

  perpendicularly
• pushing at any angle other than perpendicularly means...

  a smaller distance, and so a smaller moment
• if the total anticlockwise moment equals the total clockwise moment about the pivot...


  the object is balance and will not rotate
• levers make it easier...

  for us to do work (e.g. lift a load or turn a nut)
• gears transmit...


  rotational effects
• gears are circular discs with ... around their edges

  teeth
• the teeth of gears ... so that turning one causes another to turn, in the opposite direction

  interlock
• gears are used to...

  transmit the rotational effect of a force from one place to another
• different sized gears can be used to...

  change the moment of the force: a force transmitted to a larger gear will cause a bigger moment, as the distance of the pivot is greater
• larger gears turn ... than smaller gears

  slower