Mechanical Advantage in Sport (OCR GCSE Physical Education (PE)): Revision Note

Lever systems in sport

• A lever has a mechanical advantage if its effort arm is longer than its load arm

• A lever with mechanical advantage is more efficient and will be able to move heavier loads with relatively little effort

• We can calculate the mechanical advantage by applying the following equation: 

  mechanical advantage = effort arm length ÷ resistance arm length 

Mechanical advantage in first class levers

• First class levers must have the fulcrum nearer to the load than the effort for it to have a mechanical advantage. The nearer it is, the greater the advantage

Mechanical advantage in second class levers

• Second class levers have the best mechanical advantage as the effort is always further from the fulcrum than the load

• This means they can move a heavy load with relatively small effort  

  • E.g. at the ankle joint the effort of the gastrocnemius muscle can easily move and lift the large load of a persons body weight off the floor

Mechanical advantage in third class levers

• Third class levers are said to work at low mechanical advantage (less than 1 ) as the effort is always closer to the fulcrum than the load

• This means it requires higher effort to move a load

• Despite a mechanical disadvantage the shorter effort arm and longer load arm enables:

  • Faster movement

  • A wider range of movement

  • Light loads to move faster over greater distances

  • E.g. When swinging a baseball bat the shoulder or elbow acts as the fulcrum, with the hand applying force in the middle, while the bat (load) swings