4.2 The Lever How does a lever work?

Key Points Lever How does it work? Classes or types Mechanical advantage

Lever Made of: Lever Stiff structure that rotates around a fixed point Fulcrum Fixed point a lever rotates around Input arm Side of the lever where the input force is applied Output arm Side of the lever that moves or lifts something

Mechanical Advantage Two ways: Same formula as block and tackle MA = Li / Lo Li = Length of input arm Lo = Length of output arm

Mechanical Advantage for a Lever Formula If you know… And you need… MA = Li / Lo Length of input and output arms Mechanical advantage Li = MA * Lo Mechanical advantage and length of output arm Length of input arm Lo = Li / MA Length of input arm and mechanical advantage Length of output arm

First Class Fulcrum is between the input and output arms Examples: Spine attaches to head Vice grips Input Output Fulcrum

Second Class Output force is between the input force and the fulcrum Examples: Wheelbarrow Standing on tiptoes Output Input Fulcrum

Third Class Input force is between the output force and the fulcrum No mechanical advantage Greater speed and range of movement Example: Biceps Input Output Fulcrum