Levers

lever

rigid rod that can rotate about a fixed pivot or fulcrum when force is applied

moment arm

perpendicular distance where force acts from fulcrum

load arm

distance where load acts from fulcrum

effort arm

distance where effort acts from fulcrum

mechanical advantage

• measure of efficiency in effort required

• how much the effort-force is multiplied to overcome the load

• MA of greater than 1.0 is very efficient

mechanical advantage equation

MA = effort / load

MA = length of effort arm / length of load arm

types of levers

• 1st class lever

• 2nd class lever

• 3rd class lever

1st class lever

• fulcrum between load and effort

• very rare in human body

• MA greater or less an 1

1st class lever example

EX: neck when heading a football

• neck is fulcrum

• neck muscles is effort

• weight of head is load

2nd class lever

• the load is between effort and fulcrum

• MA greater than 1

• rare inside human body

2nd class lever example

calf muscles contracting when you stand on your toes for plantarflexion

3rd class lever

• effort between fulcrum and load

• MA less than 1

• effort arm smaller than load arm

3rd class lever example

player kicking a football during penalty kick

baseball example

• effort is the force or power used to swing bat

• fulcrum is turning point of joint where lever attaches to body

• load is what you are hitting (ball)