Chapter 8 Machines
231
Mechanical Advantage
Using a smaller effort to move a large resistance creates an advantage.
This is called the mechanical advantage of the lever.
Mechanical advantage is equal to the resistance divided by the effort.
The greater the resistance that can be moved for a given effort, the greater
the mechanical advantage is. The formula is:
Mechanical Advantage (M.A.) =
Resistance
Effort
For example, if a lever can make it possible to overcome a resistance
of 90 newtons (N) when an effort of 30 N is applied, the mechanical
advantage is 3. The newton (N) is the metric unit of force or effort.
(M.A.) = = 3
90N
30N
Fulcrum (F)
Effort (E)
Resistance (R)
gure 8-8. In a Class 2 lever,
the resistance is between the
effort and fulcrum.
Wheelbarrow
Bottle opener
Brake pedal
Nutcracker
Lifting with a plank
Switch
gure 8-9. Everyday uses of Class 2 levers.