Levers and Torque: More Practice

Classes of Levers: Student Learning Goal The 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

1 st Class Levers A 1 st class lever has the fulcrum in the centre: The fulcrum may be positioned closer to the load or closer to the effort force.

1 st Class Levers A 1 st class lever has the fulcrum in the centre: Example: a seesaw

2 nd Class Levers A 2 nd class lever has the load in the centre:

2 nd Class Levers A 2 nd class lever has the load in the centre: Example: a wheelbarrow

3 rd Class Levers A 3 rd class lever has the effort force in the centre:

3 rd Class Levers A 3 rd class lever has the effort force in the centre: Example: the human forearm

Mechanical Advantage Revisited The ideal mechanical advantage of a lever is defined as the ratio of the effort arm to the load arm:

Mechanical Advantage Revisited The ideal mechanical advantage of a lever is defined as the ratio of the effort arm to the load arm: Note that for 3 rd class levers, the IMA will be less than 1!

Mechanical Advantage Revisited The 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)

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.

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.

More Practice Three Classes of Levers Lab Activity