1. Levers and Torque: More Practice

2. Levers and Torque: More Practice

3. Levers and Torque: More Practice

4. 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).

5. Classes of Levers
SPH4C 5

6. 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.

7. 1st Class Levers A 1st class lever has the fulcrum in the centre:
Example: a seesaw

8. 2nd Class Levers
A 2nd class lever has the load in the centre:

9. 2nd Class Levers A 2nd class lever has the load in the centre:
Example: a wheelbarrow

10. 3rd Class Levers
A 3rd class lever has the effort force in the centre:

11. 3rd Class Levers A 3rd class lever has the effort force in the centre:
Example: the human forearm

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

13. 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 3rd class levers,
the IMA will be less than 1!

14. 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)

15. 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.

16. 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.

17. More Practice
Three Classes of Levers Lab Activity