LEVERS
Levers are used to apply forces. They help us to move ourselves… or other objects.
The Scientific Part!
Parts of a lever Within the lever are three components that we need to understand - Fulcrum or Pivot - the point about which the lever rotates Load or Resistance - the force applied by the lever system. Load to be moved (which includes lever itself) Effort or Force - the force applied by the user of the lever system – the force which causes movement
There are three classes of levers The class of lever is dictated by the arrangement of the 3 components:
1st Class Lever The fulcrum lies between the effort and the load e.g see-saw, crowbars
2nd Class Levers Eg wheelbarrow The load lies between the effort and the fulcrum Eg wheelbarrow
3rd Class Lever The effort lies between the load and the fulcrum Eg tweezers & most muscles.
Force Arm & Resistance Arm The distance from the fulcrum (pivot) to the point of force (effort) is called the FORCE ARM The distance from the fulcrum (pivot) to the point of resistance is called the RESISTANCE ARM Lever characteristics Long resistance arm: speed and range of movement Short resistance arm: force
FUNCTIONS OF LEVERS All levers have 2 functions: They either: Increase the speed at which an object can move with a given effort. E.g. driver as opposed to an iron in golf Increase the resistance that can be moved with a given effort E.g. Wheelbarrow – can lift a big weight that would not be able to lift alone
Mechanical advantage If Resistance arm is longer, lever is better for force If Resistance arm is shorter, lever is better for speed In 2nd class levers resistance arm is always longer, therefore 2nd class levers are better for strength or force In 3rd class levers force arm is always longer, therefore 3rd class levers are better for speed
The Application Part!
So… what happens when a golfer uses different clubs? The longer the lever the greater the speed. What about control? Which is easier to control and hit straight – an iron or a driver?
Question In badminton, why is it easier to teach children to hit the shuttle with a shorter racquet?
Debate “Short people are stronger than taller people”