2. LEVERS
• A lever is a rigid bar that rotates around a
fixed point and is used to apply force
against a resistance
• There are 3 lever systems, each containing
a fulcrum, load/resistance/weight, and
effort
• In the body the levers are the bones, the
joints are the fulcrums, the muscles act as
the effort, and the weight of the body
part and anything being held by it, is the
resistance
3. • 3 types of lever
–1st
class E F L
–2nd
class F L E
–3rd
class F E L
6. Lengths of levers
• Bones are our bodies levers
• The longer the lever the greater the change in
momentum
• This leads to an increase in speed at one end, leading
to more force being produced therefore more speed
• can you think of sporting examples both within the body
and also using equipment when the length of a lever
improves performance through an increase or decease in
momentum?
•Tennis, rowing, golf, discus, cricket…
7. Resistance arms and effort arms
3rd
class levers:
Fulcrum/pivot
Effort arm
Resistance arm
L/R/W
E
Draw the other 2 classes of levers and identify the
effort and resistance arms on each
8. Advantages and disadvantages of 2nd
class levers
DISADVANTAGES
•Small range of
movement because of
short resistance arm
•Known as “mechanical
disadvantage”
•Resistance cannot be
moved quickly because
force is applied
further away from the
fulcrum
ADVANTAGES
•Effort arm is long so
muscles able to
provide lots of force
•Known as “mechanical
advantage”
9. Advantages and disadvantages of 3rd
class levers
ADVANTAGES
•Wide range of
movement because of
long resistance arm
•Known as “mechanical
advantage”
•Resistance can be
moved quickly because
force is applied close
to the fulcrum
DISADVANTAGES
•effort arm is short
so muscles unable to
provide much force
•Known as “mechanical
disadvantage”
10. In an exam
• Identify and name the lever system
• E.g write down 3rd
class lever system
• Write in full all labels with directions
• Identify effort and resistance arms
• Give a sporting example
