Levers and Torque: More Practice
Levers and Torque: More Practice
Levers and Torque: More Practice
Classes of Levers: Student Learning GoalThe student will investigate the relationships
between force, distance, and torque for the load arm and effort arm of the three classes of levers (C2.4, C2.5).
Classes of Levers
SPH4C
1st Class Levers
A 1st class lever has the fulcrum in the centre:
The fulcrum may be positioned closer to the load or closer to the effort force.
1st Class Levers
A 1st class lever has the fulcrum in the centre:
Example: a seesaw
2nd Class Levers
A 2nd class lever has the load in the centre:
2nd Class Levers
A 2nd class lever has the load in the centre:
Example: a wheelbarrow
3rd Class Levers
A 3rd class lever has the effort force in the centre:
3rd Class Levers
A 3rd class lever has the effort force in the centre:
Example: the human forearm
Mechanical Advantage RevisitedThe ideal mechanical advantage of a lever is
defined as the ratio of the effort arm to the load arm:
L
E
d
dIMA
Mechanical Advantage RevisitedThe ideal mechanical advantage of a lever is
defined as the ratio of the effort arm to the load arm:
Note that for 3rd class levers, the IMA will be less than 1!
L
E
d
dIMA
Mechanical Advantage RevisitedThe actual mechanical advantage of a lever is
defined as the ratio of the load force to the effort force:
(and again, this may be less than 1)
E
L
F
FAMA
Mechanical Advantage Revisited
This mechanical advantage may be affected not only by friction but also by factors such as the weight of the lever itself.
E
L
F
FAMA
Efficiency
Efficiency is, as before:
Note that a lever can have a low (even less than 1) AMA and IMA but still have a high efficiency if the AMA is close to the IMA.
%100% IMA
AMAefficiency
More Practice
Three Classes of Levers Lab Activity